Scientist to Gather Greenhouse Gas Emissions from Melting Permafrost

Goddard scientist Emily Wilson poses here with an early version or prototype of her recently miniaturized laser heterodyne radiometer — an instrument for which she received a patent in 2014. Image Credit: NASA

A NASA scientist who has developed a novel suitcase-size instrument to measure column carbon dioxide and methane is taking her recently patented instrument on the road this summer to comprehensively measure emissions of these important greenhouse gases from Alaska’s melting permafrost. 

Emily Wilson, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, will use her recently patented miniaturized laser heterodyne radiometer (mini-LHR) to carry out a multi-disciplinary field campaign at three sites — each representing a different type of permafrost — near Fairbanks, Alaska, in June. Her team has designed a unique and comprehensive experiment that records permafrost depth and structure, meteorological data, and concentrations of methane and carbon dioxide during the seasonal ground melt.

Multi-Disciplinary Approach

“With the global mean temperature rising, the release of these gases could create an amplified effect,” she said. “These data will allow us to estimate fluctuation of emissions from the melting permafrost.”

Permafrost is permanently frozen soil. Comprising 24 percent of the Northern Hemisphere, permafrost contains old organic carbon deposits — some relicts from the last glaciation — that are locked up beneath the surface. Scientists have observed that more of the permafrost’s upper layer, or the active layer, is melting each summer, creating concern that the thawing could lead to the significant greenhouse-gas emissions.

Further exacerbating the situation is the fact that while methane doesn’t linger as long as carbon dioxide in the atmosphere, it is more potent and effective at absorbing heat, creating a positive feedback, where emissions leads to more warming, which in turn accelerates the thaw.

Highly portable, the mini-LDR is ideal for permafrost studies, Wilson said. Made up of commercially available components, the instrument literally can go anywhere to measure carbon dioxide and methane in the atmospheric column — that is, the levels of these gases in a vertical column extending from the ground to space. Currently, the only ground-based network that measures these two greenhouse gases in the atmospheric column is the Total Carbon Column Observing Network. However, the network has 22 operational sites globally, with limited coverage in the Arctic.

“We’re targeting areas where there is limited coverage,” she said.

To prepare for the campaign, Wilson made her instrument more rugged and more sensitive. She added a satellite communications port to remotely retrieve data, a thermally controlled instrument housing to protect the instrument from changing temperatures, and a solar grid and battery storage system for powering the instrument in remote locations.

Source: Nasa

UCLA and CASIS to collaborate on International Space Station study of possible therapy for bone loss

A study of rodents on the International Space Station will allow astronauts to test the ability of a bone-forming molecule to direct stem cells to induce bone formation. Credit: Nasa

UCLA has received grant funding from the Center for the Advancement of Science in Space to lead a research mission that will send rodents to the International Space Station. The mission will allow astronauts on the space station and scientists on Earth to test a potential new therapy for accelerating bone growth in humans. 

The research will be led by Dr. Chia Soo, a UCLA professor of plastic and reconstructive surgery and orthopaedic surgery who is member of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research. Soo also is the research director for UCLA Operation Mend, which provides medical care for wounded warriors.

The study will test the ability of a bone-forming molecule called NELL-1 to direct stem cells to induce bone formation and prevent bone degeneration. Their work will build upon previous UCLA studies that were funded by the NIH.

Other members of the UCLA research team are Dr. Kang Ting, a professor of dentistry who discovered NELL-1 and is leading efforts to translate NELL-1 therapy to humans; Dr. Ben Wu, a professor of bioengineering and dentistry who modified the NELL-1 molecule to make it useful for treating osteoporosis; and Dr. Jin Hee Kwak, an assistant professor of dentistry who will manage the study’s daily operations.

Prolonged space flights induce extreme changes in bone and organ systems that cannot be replicated on Earth.

The UCLA–ISS team, which will begin ground operations in early 2015, hopes that the study will provide new insights into the prevention of bone loss or osteoporosis as well as the regeneration of massive bone defects that can occur in wounded military personnel. Osteoporosis is a significant health issue commonly associated with “skeletal disuse” conditions such as immobilization, stroke, cerebral palsy, muscular dystrophy, spinal cord injury and jaw resorption after tooth loss.

“NELL-1 holds tremendous hope not only for preventing bone loss, but one day even restoring healthy bone,” Ting said. “For patients who are bed-bound and suffering from bone loss, it could be life-changing.” 

The UCLA team will oversee the ground operations of the mission in tandem with a flight operation coordinated by CASIS and NASA.  

“A group of 40 rodents will be sent to the International Space Station U.S. National Laboratory onboard the SpaceX Dragon capsule, where they will live for two months in a microgravity environment during the first ever test of NELL-1 in space,” said Dr. Julie Robinson, NASA’s chief scientist for the International Space Station program at the Johnson Space Center.

“CASIS is proud to work alongside UCLA in an effort to promote the station as a viable platform for bone loss inquiry,” said Warren Bates, director of portfolio management for CASIS. “Through investigations like this, we hope to make profound discoveries and enable the development of therapies to counteract bone loss ailments common in humans.”

“Besides testing the limits of NELL-1’s robust bone-producing effects, this mission will provide new insights about bone biology and could uncover important clues for curing diseases such as osteoporosis,” Wu said. 

“NIH has been pleased to work with NASA and CASIS to encourage the use of the International Space Station as a unique microgravity environment that can test innovative hypotheses that will benefit human health on Earth,” said Dr. Joan A. McGowan, director of the division of musculoskeletal diseases at the National Institute of Arthritis and Musculoskeletal and Skin Diseases, part of the NIH.

“This research has enormous translational application for astronauts in space flight and for patients on Earth who have osteoporosis or other bone-loss problems from disease, illness or trauma,” Soo said. “We very much appreciate the dedicated review staff at CASIS and the Center for Scientific Review, the portal for NIH grant applications, who made this effort possible.”

The research is supported by grants from the Center for the Advancement of Science in Space and National Institutes of Health. Additional funding and support are provided by the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, the UCLA School of Dentistry, UCLA department of orthopaedic surgery and the UCLA Orthopaedic Hospital Research Center.

Source: UCLA

Gully patterns document Martian climate cycles

Martian gullies, old and new Sharp-featured, relatively recent gullies (blue arrows) and degraded older gullies (gold) in the same location on the surface of Mars suggest multiple episodes of liquid water flow, consistent with cyclical climate change on the Red Planet. Image: NASA HiRISE

Gullies carved into impact craters on Mars provide a window into climate change on the Red Planet. A new analysis suggests Mars has undergone several ice ages in the last several million years. The driver of these climate swings is likely the Red Planet's wobbly axis tilt.

PROVIDENCE, R.I. [Brown University] — Geologists from Brown University have found new evidence that glacier-like ice deposits advanced and retreated multiple times in the midlatitude regions of Mars in the relatively recent past.

For the study, in press in the journal Icarus, the researchers looked at hundreds of gully-like features found on the walls of impact craters throughout the Martian midlatitudes. They conclude that many of those gullies were formed by meltwater from icy deposits, which are known to have covered the Martian midlatitudes within the last 2 million years. The study also turned up evidence of multiple gully-forming events, suggesting that these ice deposits waxed and waned several times over the last several million years — relatively recently in Mars’ 4.5-billion year history.

“These recent climate cycles have been predicted by computer models, but have not been documented with widespread geological evidence until now,” said Jay Dickson, a researcher at Brown and the study’s lead author. “This research shows that gullies have been episodic across the entire southern hemisphere, a distribution that is required for this to be a signal of global climate change.”

Wobbly axis

At present, most of the water ice on Mars is concentrated at its poles, but there’s a wealth of evidence that it wasn’t always that way. In 2003, research led by Brown geologists James Head and Jack Mustard showed that the midlatitude regions of Mars are draped to varying degrees by layers of ice-rich soil and dust. Landforms in and around the deposits, termed the “latitude-dependent mantle,” look remarkably similar to glacial terrains found here on Earth. The deposits suggest the presence of thin glacier-like ice deposits sometime between 400,000 and 2 million years ago.

The researchers concluded that this recent Martian ice age was likely linked to the planet’s wobbly rotation around its axis. Currently, the angle of Mars’ axis — its obliquity — is about 25 degrees, fairly close to that of Earth. But because Mars lacks a large moon to stabilize its rotation, its recent obliquity oscillates between around 15 degrees and as much as 35 degrees. (Earth’s obliquity, in contrast, varies only 2.4 degrees). Computer models predict that when the obliquity of Mars exceeds 30 degrees, increased sunlight at the poles causes water in the ice caps to be freed into the atmosphere. That water is transported and deposited closer to the equator in the form of glacial snow and ice.

Mars is known to have crossed the 30-degree threshold in obliquity several times during the last 20 million years. So if obliquity drives ice ages, there should be evidence for multiple glacial periods in the Martian midlatitudes, and that’s what the researchers were looking for in this latest study.

Gullies old and new

The researchers looked at detailed images taken by NASA’s High Resolution Imaging Science Experiment (HiRISE) of 479 gullies in the midlatitudes of Mars’ southern hemisphere. The gully systems, which form on steep crater walls, consist of an alcove at the top from which sediment is excavated, a channel through which material is carried, and a delta-like fan at the bottom where material is deposited.

The survey showed gully systems in various states of erosion and degradation. In some places, older gully fans, eroded over many years by the elements, had been crosscut by new gully fan systems. That suggests at least two gully-carving events. In other examples, gully fans were clearly visible, but the alcoves and channels that supplied them had disappeared, covered by a new layer of ice-rich soil. That too suggests multiple periods of glacial deposition.

“We show solid evidence of at least two periods of emplacement of the latitude-dependent mantle,” said Head, an author on the new paper. “That’s consistent with the idea of cyclical ice ages on Mars related to its obliquity.”

The work also bolsters the idea the many of gullies were carved by flows of liquid water. In recent years researchers have shown that some of these gully systems are still active today, when the flow of liquid water is unlikely. The present-day activity is likely driven by CO2 frost, which evaporates from the soil causing rock and rubble to slide down slopes. But this latest study shows that gullies were active when obliquity was higher and CO2 frost would have been sparse. And the association of gullies with ice-rich deposits strongly suggests that water carved these older gullies.

“We see similar features in Antarctica,” Head said. “Despite cold air temperatures, the sun is able to heat ice just enough for melting and gully activity to occur.”

This and other research pointing to relatively recent ice ages on Mars suggest the midlatitudes of Mars could be a place to look for signs of past life, Head said.

“I think people have this idea of Mars as an inactive place, that it is now as it has been for billions of years,” he said. “But it seems likely that climate cycles and global climate change are still occurring.”

Source: Brown University

Seeking reality in the future of aeronautical simulation

This CFD visualization required a NASA supercomputer to handle the intensive calculations. It shows a mesh adaptation used to simulate a transport aircraft in a high-lift configuration. Credit: NASA / Elizabeth Lee-Rausch, Michael Park

The right tool for the job. It's a platitude that is as true for garage tinkerers as it is for the NASA aeronautical innovators who are helping to design future airliners that will cut fuel consumption, reduce polluting emissions and fly more quietly.

Yet at least in one area -- namely computational fluid dynamics, or CFD -- the design tools that helped give us the modern airliners flying today are not expected to be up to the challenge in the future without some serious upgrades.

This was the finding of a report recently released by NASA called "CFD Vision 2030 Study: A Path to Revolutionary Computational Aerosciences." It came out of a one-year study funded by NASA that included Boeing, Pratt & Whitney, Stanford University, The Massachusetts Institute of Technology, The University of Wyoming and The National Center for Supercomputing Applications.

The dilemma is that today's CFD, which simulates airflow around an airplane and through its jet engines, is largely designed to deal with aircraft with traditional tube and wing configurations that everyone is used to. And even then CFD's full effectiveness through all phases of flight is limited.

But future aircraft designs routinely flying during the 2030's may look very different from today's airliners in order to deliver on the promises of reduced fuel burn, noise and emissions.

Wings may be longer and skinnier and held up, or braced, by trusses. Aircraft hulls may be broader and flatter or have more pointed noses. Jet engines may be mounted on the top of the aircraft. Or the joint between a wing and the body may be blended into a seamless contour.

Understanding the physics behind how all of these new variables will affect airflow during all phases of flight, and then finding a way to model that in a computer simulation and validate the CFD is accurate, are the challenges facing NASA's computer experts right now.

"If we can get more physics into the models we're using with our CFD, we'll have a more general tool that can attack not only off-design conditions of conventional tube and wing aircraft, but it also will do better with the different looking configurations of the future," said Mike Rogers, an aerospace engineer at NASA's Ames Research Center in California.

Data from wind-tunnel testing of these new aircraft designs as they come along will help refine the CFD algorithms. The overarching goal is to improve the entire suite of testing capabilities -simulation, ground and flight test -- to provide a more effective, comprehensive toolbox for designers to use to advance the state of the art more quickly.

"It's an iterative process," Rogers said. "We need to continually assess how well our tools are working so we know whether they are adequate or not."

In the meantime, even as NASA's CFD experts work down a path toward their long-range future goals of 2030 -- advancements made possible only because of vast leaps in computer processing speed and power -- their first step is to meet a set of more immediate technical challenges as soon as 2017.

The first stepping-stone goal is to reduce by 40 percent the error in computing several flow phenomena for which current models fail to make accurate predictions; these flow features are likely to be encountered on some of the new aircraft configurations now being studied.

The report highlighted the need for upgrading not only the CFD algorithms, but also discussed how those new algorithms must be written to take advantage of the ever-increasing speed and complexity of future supercomputers.

Source: nasa

Technology innovations spin NASA's SMAP into space

Artist's rendering of the SMAP instrument. Credit: NASA

It's active. It's passive. And it's got a big, spinning lasso.

Scheduled for launch on Jan. 29, 2015, NASA's Soil Moisture Active Passive (SMAP) instrument will measure the moisture lodged in Earth's soils with an unprecedented accuracy and resolution. The instrument's three main parts are a radar, a radiometer and the largest rotating mesh antenna ever deployed in space.

Remote sensing instruments are called "active" when they emit their own signals and "passive" when they record signals that already exist. The mission's science instrument ropes together a sensor of each type to corral the highest-resolution, most accurate measurements ever made of soil moisture -- a tiny fraction of Earth's water that has a disproportionately large effect on weather and agriculture.

To enable the mission to meet its accuracy needs while covering the globe every three days or less, SMAP engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, designed and built the largest rotating antenna that could be stowed into a space of only one foot by four feet (30 by 120 centimeters) for launch. The dish is 19.7 feet (6 meters) in diameter.

"We call it the spinning lasso," said Wendy Edelstein of NASA's Jet Propulsion Laboratory, Pasadena, California, the SMAP instrument manager. Like the cowboy's lariat, the antenna is attached on one side to an arm with a crook in its elbow. It spins around the arm at about 14 revolutions per minute (one complete rotation every four seconds). The antenna dish was provided by Northrop Grumman Astro Aerospace in Carpinteria, California. The motor that spins the antenna was provided by the Boeing Company in El Segundo, California.

"The antenna caused us a lot of angst, no doubt about it," Edelstein noted. Although the antenna must fit during launch into a space not much bigger than a tall kitchen trash can, it must unfold so precisely that the surface shape of the mesh is accurate within about an eighth of an inch (a few millimeters).

The mesh dish is edged with a ring of lightweight graphite supports that stretch apart like a baby gate when a single cable is pulled, drawing the mesh outward. "Making sure we don't have snags, that the mesh doesn't hang up on the supports and tear when it's deploying -- all of that requires very careful engineering," Edelstein said. "We test, and we test, and we test some more. We have a very stable and robust system now."

SMAP's radar, developed and built at JPL, uses the antenna to transmit microwaves toward Earth and receive the signals that bounce back, called backscatter. The microwaves penetrate a few inches or more into the soil before they rebound. Changes in the electrical properties of the returning microwaves indicate changes in soil moisture, and also tell whether or not the soil is frozen. Using a complex technique called synthetic aperture radar processing, the radar can produce ultra-sharp images with a resolution of about half a mile to a mile and a half (one to three kilometers).

SMAP's radiometer detects differences in Earth's natural emissions of microwaves that are caused by water in soil. To address a problem that has seriously hampered earlier missions using this kind of instrument to study soil moisture, the radiometer designers at NASA's Goddard Space Flight Center, Greenbelt, Maryland, developed and built one of the most sophisticated signal-processing systems ever created for such a scientific instrument.

The problem is radio frequency interference. The microwave wavelengths that SMAP uses are officially reserved for scientific use, but signals at nearby wavelengths that are used for air traffic control, cell phones and other purposes spill over into SMAP's wavelengths unpredictably. Conventional signal processing averages data over a long time period, which means that even a short burst of interference skews the record for that whole period. The Goddard engineers devised a new way to delete only the small segments of actual interference, leaving much more of the observations untouched.

Combining the radar and radiometer signals allows scientists to take advantage of the strengths of both technologies while working around their weaknesses. "The radiometer provides more accurate soil moisture but a coarse resolution of about 40 kilometers [25 miles] across," said JPL's Eni Njoku, a research scientist with SMAP. "With the radar, you can create very high resolution, but it's less accurate. To get both an accurate and a high-resolution measurement, we process the two signals together."

SMAP will be the fifth NASA Earth science mission launched within the last 12 months.
For more about the SMAP mission, visit: http://www.nasa.gov/smap/
NASA monitors Earth's vital signs from space, air and land with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.

Source: nasa

Still hot inside the Moon: Tidal heating in the deepest part of the lunar mantle

This is an artist's conception of internal structure of the Moon based on this science result.
Credit: Image courtesy of National Astronomical Observatory of Japan

An international research team, led by Dr. Yuji Harada from Planetary Science institute, China University of Geosciences, has found that there is an extremely soft layer deep inside the Moon and that heat is effectively generated in the layer by the gravity of Earth.

The results were derived by comparing the deformation of the Moon as precisely measured by Kaguya (SELENE, Selenological and Engineering Explorer) and other probes with theoretically calculated estimates. These findings suggest that the interior of the Moon has not yet cooled and hardened, and also that it is still being warmed by the effect of Earth on the Moon. This research provides a chance to reconsider how both Earth and the Moon have been evolving since their births through mutual influence until now.

When it comes to clarifying how a celestial body like a planet or a natural satellite is born and grows, it is necessary to know as precisely as possible its internal structure and thermal state. How can we know the internal structure of a celestial body far away from us? We can get clues about its internal structure and state by thoroughly investigating how its shape changes due to external forces. The shape of a celestial body being changes by the gravitational force of another body is called tide. For example, the ocean tide on Earth is one tidal phenomenon caused by the gravitational force between the Moon and the Sun, and Earth. Sea water is so deformable that its desplacement can be easily observed. How much a celestial body can be deformed by tidal force, in this way, depends on its internal structure, and especially on the hardness of its interior. Conversely, it means that observing the degree of deformation enables us to learn about the interior, which is normally not directly visible to the naked eye.

The Moon is no exception; we can learn about the interior of our natural satellite from its deformation caused by the tidal force of Earth. The deformation has already been well known through several geodetic observations (*1). However, models of the internal structure of the Moon as derived from past research could not account for the deformation precisely observed by the above lunar exploration programs.

Therefore, the research team performed theoretical calculations to understand what type of internal structure of the Moon leads to the observed change of the lunar shape.
What the research team focused on is the structure deep inside the Moon. During the Apollo program, seismic observations (*2) were carried out on the Moon. One of the analysis results concerning the internal structure of the Moon based upon the seismic data indicates that the satellite is considered to consist mainly of two parts: the "core," the inner portion made up of metal, and the "mantle," the outer portion made up of rock. The research team has found that the observed tidal deformation of the Moon can be well explained if it is assumed that there is an extremely soft layer in the deepest part of the lunar mantle. The previous studies indicated that there is the possibility that a part of the rock at the deepest part inside the lunar mantle may be molten. This research result supports the above possibility since partially molten rock becomes softer. This research has proven for the first time that the deepest part of the lunar mantle is soft, based upon the agreement between observation results and the theoretical calculations.

Furthermore, the research team also clarified that heat is efficiently generated by the tides in the soft part, deepest in the mantle. In general, a part of the energy stored inside a celestial body by tidal deformation is changed to heat. The heat generation depends on the softness of the interior. Interestingly, the heat generated in the layer is expected to be nearly at the maximum when the softness of the layer is comparable to that which the team estimated from the above comparison of the calculations and the observations. This may not be a coincidence. Rather, the layer itself is considered to be maintained as the amount of the heat generated inside the soft layer is exquisitely well balanced with that of the heat escaping from the layer. Whereas previous research also suggests that some part of the energy inside the Moon due to the tidal deformation is changed to heat, the present research indicates that this type of energy conversion does not uniformly occur in the entire Moon, but only intensively in the soft layer. The research team believes that the soft layer is now warming the core of the Moon as the core seems to be wrapped by the layer, which is located in the deepest part of the mantle, and which efficiently generates heat. They also expect that a soft layer like this may efficiently have warmed the core in the past as well.

Concerning the future outlook for this research, Dr. Yuji Harada, the principle investigator of the research team, said, "I believe that our research results have brought about new questions. For example, how can the bottom of the lunar mantle maintain its softer state for a long time? To answer this question, we would like to further investigate the internal structure and heat-generating mechanism inside the Moon in detail. In addition, another question has come up: how has the conversion from the tidal energy to the heat energy in the soft layer affected the motion of the Moon relative to the Earth, and also the cooling of the Moon? We would like to resolve those problems as well so that we can thoroughly understand how the Moon was born and has evolved."

Another investigator, Prof. Junichi Haruyama of Institute of Space and Aeronautical Science, Japan Aerospace Exploration Agency, mentioned the significance of this research, saying, "A smaller celestial body like the Moon cools faster than a larger one like the Earth does. In fact, we had thought that volcanic activities on the Moon had already come to a halt. 

Therefore, the Moon had been believed to be cool and hard, even in its deeper parts. However, this research tells us that the Moon has not yet cooled and hardened, but is still warm. It even implies that we have to reconsider the question as follows: How have the Earth and the Moon influenced each other since their births? That means this research not only shows us the actual state of the deep interior of the Moon, but also gives us a clue for learning about the history of the system including both the Earth and the Moon."

The scientific paper on which this article is based appears in the Nature Geoscience.

Strong tidal heating in an ultralow-viscosity zone at the core-mantle boundary of the Moon.
Note:
*1: Geodetic observation. (This is also called "selenodetic" observation as it is for the Moon.)
Observational results on gravity and rotation of the Moon are used in this research. Precise measurements of the lunar gravity and rotation enable us to know how our natural satellite is deformed by tidal forces.

The gravity of the Moon can be measured by tracking the motion of a satellite orbiting the Moon. This is because the motion of the satellite is influenced by lunar gravity. The motion of the satellite orbiting the Moon can be determined by using radio waves between the Earth and the satellite, and between multiple satellites around the Moon. The gravity of the Moon changes when it deforms due to tidal forces. The change in gravity caused by the lunar deformation due to the tidal force is extremely small, but when the change in location of the orbiter can be determined precisely enough, it is possible to accurately detect the change in lunar gravity caused by the deformation due to the tidal force. During the last several years, the degree of the lunar deformation caused by the tidal forces has been determined by several orbiters, for example, Kaguya from Japan, Chang'e-1 from China, and Lunar Reconnaissance Orbiter (LRO) and Gravity Recovery and Interior Laboratory (GRAIL) from the USA.

The rotation of the Moon can be observed by monitoring the change in position of a kind of mirror placed in several locations on the lunar surface. The same side of the Moon is almost always facing the Earth, but strictly speaking, it changes by a slight amount according to the lunar orbit around the Earth. This means that the locations of the mirrors with respect to the Earth also changes over time. If this change in position is precisely measured, it can also be determined how the direction of the lunar axis changes. This slight change of direction also depends on the deformation caused by the tidal force. It can be seen, therefore, how the Moon deforms due to the tidal force once the change in the axis is measured precisely. Some of the above-mentioned mirrors have been left on the surface of the Moon in the framework of the lunar exploration programs led by the USA or the former USSR several decades ago, such as the Apollo program. The degree of change in the location of each mirror on the Moon can be determined by using laser beams emitted from the Earth. This experiment still continues to be carried out even today.

*2: Seismic observation. (Quakes on the Moon are also called "moonquakes." )

There are seismic activities not only on the Earth, but also on the Moon. As part of the Apollo program in the past, seismometers were placed on the lunar surface for seismological measurements. Waves induced by quakes measured with seismometers suggest what the internal structure of a celestial body is like. The behavior of the seismic waves is very important for understanding how the hardness inside the celestial body will change in accordance with the depth. In particular, the present research considered the following two previous analysis results in order to theoretically calculate the lunar deformation caused by the tidal force.

The first one is the existence of the area deep inside the Moon where the seismic waves become drastically weaker. It is generally known that the energy of the seismic waves tends to reduce more in softer solids, especially when they contain liquids. Therefore, the deepest part of the lunar mantle is softer than the shallower part. Also, a portion of the rocks is thought to be melted.

The second one is the existence of areas deep inside the Moon whose interfaces reflect the 
seismic waves. Three boundaries are considered to exist. Two of them are like the ones in the Earth: one separating the solid inner core and the liquid outer core, and the other one separating the outer core and the mantle. The last boundary is considered to correspond to the one in the mantle separating the solid area and the partially molten area mentioned above.

Source: National Astronomical Observatory of Japan

Solving the mystery of the 'Man in the Moon': Volcanic plume, not an asteroid, likely created the moon's largest basin

The moon as observed in visible light (left), topography (center, where red is high and blue is low), and the GRAIL gravity gradients (right). The Procellarum region is a broad region of low topography covered in dark mare basalt. The gravity gradients reveal a giant rectangular pattern of structures surrounding the region. Credit: NASA/Colorado School of Mines/MIT/JPL/Goddard Space Flight Center

New data obtained by NASA's GRAIL mission reveals that the Procellarum region on the near side of the moon -- a giant basin often referred to as the "man in the moon" -- likely arose not from a massive asteroid strike, but from a large plume of magma deep within the moon's interior.

The Procellarum region is a roughly circular, volcanic terrain some 1,800 miles in diameter -- nearly as wide as the United States. One hypothesis suggested that it was formed by a massive impact, in which case it would have been the largest impact basin on the moon. Subsequent asteroid collisions overprinted the region with smaller -- although still large -- basins.

Now researchers from MIT, the Colorado School of Mines, and other institutions have created a high-resolution map of the Procellarum, and found that its border is not circular, but polygonal, composed of sharp angles that could not have been created by a massive asteroid. Instead, researchers believe that the angular outline was produced by giant tension cracks in the moon's crust as it cooled around an upwelling plume of hot material from the deep interior.

Maria Zuber, the E.A. Griswold Professor of Geophysics and also MIT's vice president for research, says that as cracks occurred, they formed a "plumbing system" in the moon's crust through which magma could meander to the surface. Magma eventually filled the region's smaller basins, creating what we see today as dark spots on the near side of the moon -- features that have inspired the popular notion of a "man in the moon."

"A lot of things in science are really complicated, but I've always loved to answer simple questions," says Zuber, who is principal investigator for the GRAIL (Gravity Recovery and Interior Laboratory) mission. "How many people have looked up at the moon and wondered what produced the pattern we see -- let me tell you, I've wanted to solve that one!"

Zuber and her colleagues publish their results this week in the journal Nature.

Making Less of an Impact

The team mapped the Procellarum region using data obtained by GRAIL -- twin probes that orbited the moon from January to December 2012. Researchers measured the distance between the probes as they chased each other around the moon. As the leading probe passed over a region of lower density, it briefly slowed, caught by that region's gravitational pull. As the probes circled the moon, they moved in accordion fashion, the distance between them stretching and contracting in response to varying gravitational attraction due to the mass variations in the lunar interior.

From the variable distance between the probes, Zuber and her team determined the strength of gravity across the moon's surface, creating a highly detailed map, which they then used to determine where the lunar crust thickens and thins.

From this mapping, the researchers observed that the rim of the Procellarum region is composed of edges that abut at 120-degree angles. As asteroid impacts tend to produce circular or elliptical craters, Zuber says the Procellarum's angular shape could not have been caused by an impact.

Instead, the team explored an alternative scenario: Some time after the moon formed and cooled, a large plume of molten material rose from the lunar interior, around where the Procellarum region is today. The steep difference in temperature between the magma plume and the surrounding crust caused the surface to contract over time, creating a pattern of fractures that provided a conduit for molten material to rise to the surface.

To test the hypothesis, the researchers modeled the region's gravitational signal if it were to contain volcanic intrusions -- magma that seeped up to just beneath the moon's surface and, over time, cooled and crystallized. The resulting simulation matched the gravity signal recorded by GRAIL, supporting the idea that the Procellarum was caused by a magma plume, and not an asteroid.

"How such a plume arose remains a mystery," Zuber says. "It could be due to radioactive decay of heat-producing elements in the deep interior. Or, conceivably, a very early large impact triggered the plume. But in the latter case, all evidence for such an impact has been completely erased. People who thought that all this volcanism was related to a gigantic impact need to go back and think some more about that."

Source: Nasa

Earth-like soils on Mars? Ancient fossilized soils potentially found deep inside impact crater suggest microbial life

Rover image from Gale Crater reveals soil features similar to paleosols on Earth. Credit: NASA

Soil deep in a crater dating to some 3.7 billion years ago contains evidence that Mars was once much warmer and wetter, saysUniversity of Oregon geologist Gregory Retallack, based on images and data captured by the rover Curiosity.

NASA rovers have shown Martian landscapes littered with loose rocks from impacts or layered by catastrophic floods, rather than the smooth contours of soils that soften landscapes on Earth. However, recent images from Curiosity from the impact Gale Crater, Retallack said, reveal Earth-like soil profiles with cracked surfaces lined with sulfate, ellipsoidal hollows and concentrations of sulfate comparable with soils in Antarctic Dry Valleys and Chile's Atacama Desert.

His analyses appear in a paper placed online this week by the journal Geology in advance of print in the September issue of the world's top-ranked journal in the field. Retallack, the paper's lone author, studied mineral and chemical data published by researchers closely tied with the Curiosity mission. Retallack, professor of geological sciences and co-director of paleontology research at the UO Museum of Natural and Cultural History, is an internationally known expert on the recognition of paleosols -- ancient fossilized soils contained in rocks.

"The pictures were the first clue, but then all the data really nailed it," Retallack said. "The key to this discovery has been the superb chemical and mineral analytical capability of the Curiosity Rover, which is an order of magnitude improvement over earlier generations of rovers. The new data show clear chemical weathering trends, and clay accumulation at the expense of the mineral olivine, as expected in soils on Earth. Phosphorus depletion within the profiles is especially tantalizing, because it attributed to microbial activity on Earth."

The ancient soils, he said, do not prove that Mars once contained life, but they do add to growing evidence that an early wetter and warmer Mars was more habitable than the planet has been in the past 3 billion years.

Curiosity rover is now exploring topographically higher and geologically younger layers within the crater, where the soils appear less conducive to life. For a record of older life and soils on Mars, Retallack said, new missions will be needed to explore older and more clayey terrains.

Surface cracks in the deeply buried soils suggest typical soil clods. Vesicular hollows, or rounded holes, and sulfate concentrations, he said, are both features of desert soils on Earth.

"None of these features is seen in younger surface soils of Mars," Retallack said. "The exploration of Mars, like that of other planetary bodies, commonly turns up unexpected discoveries, but it is equally unexpected to discover such familiar ground."

The newly discovered soils provide more benign and habitable soil conditions than known before on Mars. Their dating to 3.7 billion years ago, he noted, puts them into a time of transition from "an early benign water cycle on Mars to the acidic and arid Mars of today." 

Life on Earth is believed to have emerged and began diversifying about 3.5 billion years ago, but some scientists have theorized that potential evidence that might take life on Earth farther back was destroyed by plate tectonics, which did not occur on Mars.

In an email, Malcolm Walter of the Australian Centre for Astrobiology, who was not involved in the research, said the potential discovery of these fossilized soils in the Gale Crater dramatically increases the possibility that Mars has microbes. "There is a real possibility that there is or was life on Mars," he wrote.

Retallack noted that Steven Benner of the Westheimer Institute of Science and Technology in Florida has speculated that life is more likely to have originated on a soil planet like Mars than a water planet like Earth. In an email, Benner wrote that Retallack's paper "shows not only soils that might be direct products of an early Martian life, but also the wet-dry cycles that many models require for the emergence of life."

Source: University of Oregon

Dawn spacecraft begins approach to dwarf planet Ceres

This artist's concept shows NASA's Dawn spacecraft heading toward the dwarf planet Ceres. Credit: NASA/JPL-Caltech

NASA's Dawn spacecraft has entered an approach phase in which it will continue to close in on Ceres, a Texas-sized dwarf planet never before visited by a spacecraft. Dawn launched in 2007 and is scheduled to enter Ceres orbit in March 2015.

Dawn recently emerged from solar conjunction, in which the spacecraft is on the opposite side of the sun, limiting communication with antennas on Earth. Now that Dawn can reliably communicate with Earth again, mission controllers have programmed the maneuvers necessary for the next stage of the rendezvous, which they label the Ceres approach phase. Dawn is currently 400,000 miles (640,000 kilometers) from Ceres, approaching it at around 450 miles per hour (725 kilometers per hour).

The spacecraft's arrival at Ceres will mark the first time that a spacecraft has ever orbited two solar system targets. Dawn previously explored the protoplanet Vesta for 14 months, from 2011 to 2012, capturing detailed images and data about that body.

"Ceres is almost a complete mystery to us," said Christopher Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. "Ceres, unlike Vesta, has no meteorites linked to it to help reveal its secrets. All we can predict with confidence is that we will be surprised."

The two planetary bodies are thought to be different in a few important ways. Ceres may have formed later than Vesta, and with a cooler interior. Current evidence suggests that Vesta only retained a small amount of water because it formed earlier, when radioactive material was more abundant, which would have produced more heat. Ceres, in contrast, has a thick ice mantle and may even have an ocean beneath its icy crust.

Ceres, with an average diameter of 590 miles (950 kilometers), is also the largest body in the asteroid belt, the strip of solar system real estate between Mars and Jupiter. By comparison, Vesta has an average diameter of 326 miles (525 kilometers), and is the second most massive body in the belt.

The spacecraft uses ion propulsion to traverse space far more efficiently than if it used chemical propulsion. In an ion propulsion engine, an electrical charge is applied to xenon gas, and charged metal grids accelerate the xenon particles out of the thruster. These particles push back on the thruster as they exit, creating a reaction force that propels the spacecraft. Dawn has now completed five years of accumulated thrust time, far more than any other spacecraft.

"Orbiting both Vesta and Ceres would be truly impossible with conventional propulsion. Thanks to ion propulsion, we're about to make history as the first spaceship ever to orbit two unexplored alien worlds," said Marc Rayman, Dawn's chief engineer and mission director, based at NASA's Jet Propulsion Laboratory in Pasadena, California.

The next couple of months promise continually improving views of Ceres, prior to Dawn's arrival. By the end of January, the spacecraft's images and other data will be the best ever taken of the dwarf planet.

The Dawn mission to Vesta and Ceres is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington. 

UCLA is responsible for overall Dawn mission science.

Source: NASA/Jet Propulsion Laboratory

NASA's Chandra X-ray Observatory celebrates 15th anniversary

To celebrate Chandra's 15th anniversary, four newly processed images of supernova remnants have been released. Credit: NASA/CXC/SAO

Fifteen years ago, NASA's Chandra X-ray Observatory was launched into space aboard the Space Shuttle Columbia. Since its deployment on July 23, 1999, Chandra has helped revolutionize our understanding of the universe through its unrivaled X-ray vision.

Chandra, one of NASA's current "Great Observatories," along with the Hubble Space Telescope and Spitzer Space Telescope, is specially designed to detect X-ray emission from hot and energetic regions of the universe.

With its superb sensitivity and resolution, Chandra has observed objects ranging from the closest planets and comets to the most distant known quasars. It has imaged the remains of exploded stars, or supernova remnants, observed the region around the supermassive black hole at the center of the Milky Way, and discovered black holes across the universe. Chandra also has made a major advance in the study of dark matter by tracing the separation of dark matter from normal matter in collisions between galaxy clusters. It is also contributing to research on the nature of dark energy.

To celebrate Chandra's 15th anniversary, four new images of supernova remnants -- the Crab Nebula, Tycho, G292.0+1.8, and 3C58 -- are being released. These supernova remnants are very hot and energetic and glow brightly in X-ray light, which allows Chandra to capture them in exquisite detail.

"Chandra changed the way we do astronomy. It showed that precision observation of the X-rays from cosmic sources is critical to understanding what is going on," said Paul Hertz, NASA's Astrophysics Division director in Washington. "We're fortunate we've had 15 years -- so far -- to use Chandra to advance our understanding of stars, galaxies, black holes, dark energy, and the origin of the elements necessary for life."

Chandra orbits far above Earth's X-ray absorbing atmosphere at an altitude up to 139,000 km (86,500 mi), allowing for long observations unobscured by Earth's shadow. When it was carried into space in 1999, it was the largest satellite ever launched by the shuttle.

"We are thrilled at how well Chandra continues to perform," said Belinda Wilkes, director of the Chandra X-ray Center (CXC) in Cambridge, Massachusetts. "The science and operations teams work very hard to ensure that Chandra delivers its astounding results, just as it has for the past decade and a half. We are looking forward to more ground-breaking science over the next decade and beyond."

Originally called the Advanced X-ray Astrophysics Facility (AXAF), the telescope was first proposed to NASA in 1976. Prior to its launch aboard the shuttle, the observatory was renamed in honor of the late Indian-American Nobel laureate, Subrahmanyan Chandrasekhar. Known to the world as Chandra (which means "moon" or "luminous" in Sanskrit), he was widely regarded as one of the foremost astrophysicists of the 20th century.

"Chandra continues to be one of the most successful missions that NASA has ever flown as measured against any metric -- cost, schedule, technical success and, most of all, scientific discoveries," said Martin Weisskopf, Chandra Project Scientist at the Marshall Space Flight Center in Huntsville, Ala. "It has been a privilege to work on developing and maintaining this scientific powerhouse, and we look forward to many years to come."

To help celebrate this anniversary, Chandra scientists -- including former CXC Director, Harvey Tananbaum -- will participate in a Google+ Hangout July 22 beginning at 3 p.m. EDT. For more information on this event, visit: http://go.nasa.gov/1jXcXYT

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Source: NASA

Astronomers bring the third dimension to a doomed star's outburst

A new shape model of the Homunculus Nebula reveals protrusions, trenches, holes and irregularities in its molecular hydrogen emission. The protrusions appear near a dust skirt seen at the nebula's center in visible light (inset) but not found in this study, so they constitute different structures. Credit: NASA Goddard (inset: NASA, ESA, Hubble SM4 ERO Team)

In the middle of the 19th century, the massive binary system Eta Carinae underwent an eruption that ejected at least 10 times the sun's mass and made it the second-brightest star in the sky. Now, a team of astronomers has used extensive new observations to create the first high-resolution 3-D model of the expanding cloud produced by this outburst.

"Our model indicates that this vast shell of gas and dust has a more complex origin than is generally assumed," said Thomas Madura, a NASA Postdoctoral Program fellow at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and a member of the study team. "For the first time, we see evidence suggesting that intense interactions between the stars in the central binary played a significant role in sculpting the nebula we see today."

Eta Carinae lies about 7,500 light-years away in the southern constellation of Carina and is one of the most massive binary systems astronomers can study in detail. The smaller star is about 30 times the mass of the sun and may be as much as a million times more luminous. The primary star contains about 90 solar masses and emits 5 million times the sun's energy output. Both stars are fated to end their lives in spectacular supernova explosions.

Between 1838 and 1845, Eta Carinae underwent a period of unusual variability during which it briefly outshone Canopus, normally the second-brightest star. As a part of this event, which astronomers call the Great Eruption, a gaseous shell containing at least 10 and perhaps as much as 40 times the sun's mass was shot into space. This material forms a twin-lobed dust-filled cloud known as the Homunculus Nebula, which is now about a light-year long and continues to expand at more than 1.3 million mph (2.1 million km/h).

Using the European Southern Observatory's Very Large Telescope and its X-Shooter spectrograph over two nights in March 2012, the team imaged near-infrared, visible and ultraviolet wavelengths along 92 separate swaths across the nebula, making the most complete spectral map to date. The researchers have used the spatial and velocity information provided by this data to create the first high-resolution, fully 3-D model of the Homunculus Nebula. The new model contains none of the assumptions about the cloud's symmetry found in previous studies.

The shape model, which is now published by the journal Monthly Notices of the Royal Astronomical Society, was developed using only a single emission line of near-infrared light emitted by molecular hydrogen gas. The characteristic 2.12-micron light shifts in wavelength slightly depending on the speed and direction of the expanding gas, allowing the team to probe even dust-obscured portions of the Homunculus that face away from Earth.

"Our next step was to process all of this using 3-D modeling software I developed in collaboration with Nico Koning from the University of Calgary in Canada. The program is simply called 'Shape,' and it analyzes and models the three-dimensional motions and structure of nebulae in a way that can be compared directly with observations," said lead researcher Wolfgang Steffen, an astrophysicist at the Ensenada campus of the National Autonomous University of Mexico.

The new shape model confirms several features identified by previous studies, including pronounced holes located at the ends of each lobe and the absence of any extended molecular hydrogen emission from a dust skirt apparent in visible light near the center of the nebula. New features include curious arm-like protrusions emanating from each lobe near the dust skirt; vast, deep trenches curving along each lobe; and irregular divots on the side facing away from Earth.

"One of the questions we set out to answer with this study is whether the Homunculus contains any imprint of the star's binary nature, since previous efforts to explain its shape have assumed that both lobes were more or less identical and symmetric around their long axis," explained team member Jose Groh, an astronomer at Geneva University in Switzerland. "The new features strongly suggest that interactions between Eta Carinae's stars helped mold the Homunculus."

Every 5.5 years, when their orbits carry them to their closest approach, called periastron, the immense and brilliant stars of Eta Carinae are only as far apart as the average distance between Mars and the sun. Both stars possess powerful gaseous outflows called stellar winds, which constantly interact but do so most dramatically during periastron, when the faster wind from the smaller star carves a tunnel through the denser wind of its companion. The opening angle of this cavity closely matches the length of the trenches (130 degrees) and the angle between the arm-like protrusions (110 degrees), indicating that the Homunculus likely continues to carry an impression from a periastron interaction around the time of the Great Eruption.

Once the researchers had developed their Homunculus model, they took things one step further. They converted it to a format that can be used by 3-D printers and made the file available along with the published paper.

"Now anyone with access to a 3-D printer can produce their own version of this incredible object," said Goddard astrophysicist Theodore Gull, who is also a co-author of the paper. 

"While 3-D-printed models will make a terrific visualization tool for anyone interested in astronomy, I see them as particularly valuable for the blind, who now will be able to compare embossed astronomical images with a scientifically accurate representation of the real thing."

Source: NASA

Tales from a Martian rock: New chemical analysis of ancient Martian meteorite provides clues to planet's history of habitability

The surface of Mars was once wet, but no water flows there now. UC San Diego chemists and others took a close look at meteorite that may have been blasted from this huge rift across the planet’s surface. The image is a composite of hundreds of photos taken by NASA’s Viking missions in the 1970s. Credit: USGS, NASA

A new analysis of a Martian rock that meteorite hunters plucked from an Antarctic ice field 30 years ago this month reveals a record of the planet's climate billions of years ago, back when water likely washed across its surface and any life that ever formed there might have emerged.

Scientists from the University of California, San Diego, NASA and the Smithsonian Institution report detailed measurements of minerals within the meteorite in the early online edition of the Proceedings of the National Academy of Sciences this week.

"Minerals within the meteorite hold a snapshot of the planet's ancient chemistry, of interactions between water and atmosphere," said Robina Shaheen, a project scientist at UC San Diego and the lead author of the report.

The unlovely stone, which fell to Earth 13 thousand years ago, looked a lot like a potato and has quite a history. Designated ALH84001, it is the oldest meteorite we have from Mars, a chunk of solidified magma from a volcano that erupted four billion years ago. Since then something liquid, probably water, seeped through pores in the rock and deposited globules of carbonates and other minerals.

The carbonates vary subtly depending on the sources of their carbon and oxygen atoms. Both carbon and oxygen occur in heavier and lighter versions, or isotopes. The relative abundances of isotopes forms a chemical signature that careful analysis and sensitive measurements can uncover.

Mars's atmosphere is mostly carbon dioxide but contains some ozone. The balance of oxygen isotopes within ozone are strikingly weird with enrichment of heavy isotopes through a physical chemical phenomenon first described by co-author Mark Thiemens, a professor of chemistry at UC San Diego, and colleagues 25 years ago.

"When ozone reacts with carbon dioxide in the atmosphere, it transfers its isotopic weirdness to the new molecule," said Shaheen, who investigated this process of oxygen isotope exchange as a graduate student at the University of Heidelberg in Germany. When carbon dioxide reacts with water to make carbonates, the isotopic signature continues to be preserved.

The degree of isotopic weirdness in the carbonates reflects how much water and ozone was present when they formed. It's a record of climate 3.9 billion years ago, locked in a stable mineral. The more water, the smaller the weird ozone signal.

This team measured a pronounced ozone signal in the carbonates within the meteorite, suggesting that although Mars had water back then, vast oceans were unlikely. Instead, the early Martian landscape probably held smaller seas.

"What's also new is our simultaneous measurements of carbon isotopes on the same samples. The mix of carbon isotopes suggest that the different minerals within the meteorite had separate origins," Shaheen said. "They tell us the story of the chemical and isotopic compositions of the atmospheric carbon dioxide."

ALH84001 held tiny tubes of carbonate that some scientists saw as potential evidence of microbial life, though a biological origin for the structures has been discarded. On December 16, NASA announced another potential whiff of Martian life in the form of methane sniffed by the rover Curiosity.

Carbonates can be deposited by living things that scavenge the minerals to build their skeletons, but that is not the case for the minerals measured by this team. 

"The carbonate we see is not from living things," Shaheen said. "It has anomalous oxygen isotopes that tell us this carbonate is abiotic."

By measuring the isotopes in multiple ways, the chemists found carbonates depleted in carbon-13 and enriched in oxygen-18. That is, Mars's atmosphere in this era, a period of great bombardment, had much less carbon-13 than it does today.

The change in relative abundances of carbon and oxygen isotopes may have occurred through extensive loss of Martian atmosphere. A thicker atmosphere would likely have been required for liquid water to flow on the planet's chilly surface.

"We now have a much deeper and specific insight into the earliest oxygen-water system in the solar system," Thiemens said. "The question that remains is when did planets, Earth and Mars, get water, and in the case of Mars, where did it go? We've made great progress, but still deep mysteries remain."

Source: University of California - San Diego

Gecko grippers get a microgravity test flight

Scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, are working on adhesive gripping tools that could grapple objects such as orbital debris or defunct satellites that would otherwise be hard to handle.
Credit: Image courtesy of NASA/Jet Propulsion Laboratory

There are no garbage trucks equipped to leave the atmosphere and pick up debris floating around Earth. But what if we could send a robot to do the job?

Scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, are working on adhesive gripping tools that could grapple objects such as orbital debris or defunct satellites that would otherwise be hard to handle.

The gecko gripper project was selected for a test flight through the Flight Opportunities Program of NASA's Space Technology Mission Directorate. As a test, researchers used the grippers in brief periods of weightlessness aboard NASA's C-9B parabolic flight aircraft in August.

"Orbital debris is a serious risk to spacecraft, including the International Space Station," said Aaron Parness, a JPL robotics researcher who is the principal investigator for the grippers. "This is definitely a problem we're going to have to deal with. Our system might one day contribute to a solution."

The gripping system developed by Parness and colleagues was inspired by geckos, lizards that cling to walls with ease. Geckos' feet have branching arrays of tiny hairs, the smallest of which are hundreds of times thinner than a human hair. This system of hairs can conform to a rough surface without a lot of force. Although researchers cannot make a perfect replica of the gecko foot, they have put "hair" structures on the adhesive pads of the grippers.

The synthetic hairs, also called stalks, are wedge-shaped and have a slanted, mushroom-shaped cap. When the gripping pad lightly touches part of an object, only the very tips of the hairs make contact with that surface.

"The stickiness of the grippers can be turned on and off, by changing the direction in which you pull the hairs," Parness said.

To get the gripper to stick to a surface, force is applied to the adhesive pad material in a manner that makes the hairs bend. This increases the real area of contact between the hairs and the surface, which corresponds to greater adhesion. When the force is relaxed and the hairs go back to being upright, this process turns off the stickiness.

A phenomenon called van der Waals forces, named for Nobel Prize-winning physicist Johannes Diderik van der Waals, explains the non-permanent stickiness of the grippers, as well as gecko feet. These temporary adhesive forces happen because electrons orbiting the nuclei of atoms are not evenly spaced, creating a slight electrical charge. Such forces persist even in extreme temperature, pressure and radiation conditions.

"The reliability of van der Waals forces, even in severe environments, makes them particularly useful for space applications," Parness said.

"The system could grapple objects in space that are spinning or tumbling, and would otherwise be hard to target," he said.

In the recent tests, the grippers were able to grapple a 20-pound cube as it floated. The grippers also were able to grapple a researcher wearing a vest made of spacecraft material panels, representing a 250-pound "object." 

Members of the research team held the device with adhesive pads during the test, but the eventual idea is to integrate the grippers into a robotic arm or leg.

In total, the grippers have been tested on more than 30 spacecraft surfaces at JPL. They also have been tested successfully in a JPL thermal vacuum chamber, with total vacuum conditions and temperatures of minus 76 degrees Fahrenheit (minus 60 degrees Celsius) to simulate the conditions of space. While Parness was in graduate school at Stanford University in Palo Alto, California, the grippers were tested separately in more than 30,000 cycles of "on" and "off," with the adhesive staying strong. Several prototypes have since been designed.

There are more than 21,000 pieces of orbital debris larger than 3.9 inches (10 centimeters) in Earth's orbit. The U.S. Space Surveillance Network routinely tracks these objects. In 2009, an accidental collision occurred between an operational communications satellite and a large piece of debris, destroying the satellite.

Besides grappling orbital debris, the grippers could help inspect spacecraft or assist small satellites in docking to the International Space Station. The grippers are another example of how technology drives exploration.

The California Institute of Technology manages JPL for NASA.

Source: NASA/Jet Propulsion Laboratory