New instrument reveals recipe for other Earths

How do you make an Earth-like planet? The 'test kitchen' of Earth has given us a detailed recipe, but it wasn't clear whether other planetary systems would follow the same formula. Now, astronomers have found evidence that the recipe for Earth also applies to terrestrial exoplanets orbiting distant stars. Credit: David A. Aguilar (CfA)

How do you make an Earth-like planet? The "test kitchen" of Earth has given us a detailed recipe, but it wasn't clear whether other planetary systems would follow the same formula. Now, astronomers have found evidence that the recipe for Earth also applies to terrestrial exoplanets orbiting distant stars.

"Our solar system is not as unique as we might have thought," says lead author Courtney Dressing of the Harvard-Smithsonian Center for Astrophysics (CfA). "It looks like rocky exoplanets use the same basic ingredients."

Dressing presented the research today at a meeting of the American Astronomical Society.

The key to the discovery was the HARPS-North instrument on the 3.6-meter Telescopio Nazionale Galileo in the Canary Islands. (HARPS stands for High-Accuracy Radial velocity Planet Searcher.) It is designed to accurately measure the masses of small, Earth-sized worlds. Those measurements are crucial to determine densities and therefore compositions.

"Our strategy for using HARPS-North over the past year has been to focus on planets less than two times the diameter of Earth and to study a few planets really well," explains Harvard astronomer David Charbonneau (CfA), who currently heads up the HARPS-North Science Team.

Most recently the team targeted Kepler-93b, a planet 1.5 times the size of Earth in a tight, 4.7-day orbit around its star. The mass and composition of this world were uncertain. HARPS-North nailed the mass at 4.02 times Earth, meaning that the planet has a rocky composition.

The researchers then compared all ten known exoplanets with a diameter less than 2.7 times Earth's that had accurately measured masses. They found that the five planets with diameters smaller than 1.6 times Earth showed a tight relationship between mass and size. Moreover, Venus and Earth fit onto the same line, suggesting that all these worlds have similar rock-iron compositions.

As for the larger and more massive exoplanets, their densities proved to be significantly lower, meaning that they include a large fraction of water or other volatiles, hydrogen and/or helium. They also showed more diverse compositions rather than fitting into a single group like the smaller terrestrial worlds.

The team also noted that not all planets less than six times the mass of Earth are rocky. Some low-mass worlds with very low densities are known (such as the planets in the Kepler-11 system). But for typical close-in small planets, the chances are high that they share an Earth-like composition.

"To find a truly Earth-like world, we should focus on planets less than 1.6 times the size of 

Earth, because those are the rocky worlds," recommends Dressing.

Making Other Earths

Makes one small model planet

Ingredients:

• 1 cup magnesium
• 1 cup silicon
• 2 cups iron
• 2 cups oxygen
• 1/2 teaspoon aluminum
• 1/2 teaspoon nickel
• 1/2 teaspoon calcium
• 1/4 teaspoon sulfur
• dash of water delivered by asteroids

Blend well in a large bowl, shape into a round ball with your hands and place it neatly in a habitable zone area around a young star. Do not over mix. Heat until mixture becomes a white hot glowing ball. Bake for a few million years. Cool until color changes from white to yellow to red and a golden-brown crust forms. It should not give off light anymore. Season with a dash of water and organic compounds. It will shrink a bit as steam escapes and clouds and oceans form. Stand back and wait a few more million years to see what happens. If you are lucky, a thin frosting of life may appear on the surface of your new world.

Source: Harvard-Smithsonian Center for Astrophysics

Super-Earths have long-lasting oceans

This artist's depiction shows a gas giant planet rising over the horizon of an alien waterworld. New research shows that oceans on super-Earths, once established, can last for billions of years.
Credit: David A. Aguilar (CfA)

For life as we know it to develop on other planets, those planets would need liquid water, or oceans. Geologic evidence suggests that Earth's oceans have existed for nearly the entire history of our world. But would that be true of other planets, particularly super-Earths? New research suggests the answer is yes and that oceans on super-Earths, once established, can last for billions of years.

"When people consider whether a planet is in the habitable zone, they think about its distance from the star and its temperature. However, they should also think about oceans, and look at super-Earths to find a good sailing or surfing destination," says lead author Laura Schaefer of the Harvard-Smithsonian Center for Astrophysics (CfA).

Schaefer presented her findings today in a press conference at a meeting of the American Astronomical Society.

Even though water covers 70 percent of Earth's surface, it makes up a very small fraction of the planet's overall bulk. Earth is mostly rock and iron; only about a tenth of a percent is water.

"Earth's oceans are a very thin film, like fog on a bathroom mirror," explains study co-author Dimitar Sasselov (CfA).

However, Earth's water isn't just on the surface. Studies have shown that Earth's mantle holds several oceans' worth of water that was dragged underground by plate tectonics and subduction of the ocean seafloor. Earth's oceans would disappear due to this process, if it weren't for water returning to the surface via volcanism (mainly at mid-ocean ridges). Earth maintains its oceans through this planet-wide recycling.

Schaefer used computer simulations to see if this recycling process would take place on super-Earths, which are planets up to five times the mass, or 1.5 times the size, of Earth. She also examined the question of how long it would take oceans to form after the planet cooled enough for its crust to solidify.

She found that planets two to four times the mass of Earth are even better at establishing and maintaining oceans than our Earth. The oceans of super-Earths would persist for at least 10 billion years (unless boiled away by an evolving red giant star).

Interestingly, the largest planet that was studied, five times the mass of Earth, took a while to get going. Its oceans didn't develop for about a billion years, due to a thicker crust and lithosphere that delayed the start of volcanic outgassing.

"This suggests that if you want to look for life, you should look at older super-Earths," Schaefer says.

Sasselov agrees. "It takes time to develop the chemical processes for life on a global scale, and time for life to change a planet's atmosphere. So, it takes time for life to become detectable."

This also suggests that, assuming evolution takes place at a similar rate to Earth's, you want to search for complex life on planets that are about five and a half billion years old, a billion years older than Earth.

Source: Harvard-Smithsonian Center for Astrophysics

DNA survives critical entry into Earth's atmosphere

This image shows the launch of the rocket TEXUS-49 from the Esrange Space Center in Kiruna, North Sweden. Credit: Adrian Mettauer

The genetic material DNA can survive a flight through space and re-entry into Earth's atmosphere -- and still pass on genetic information. A team of scientists from UZH obtained these astonishing results during an experiment on the TEXUS-49 research rocket mission.

Applied to the outer shell of the payload section of a rocket using pipettes, small, double-stranded DNA molecules flew into space from Earth and back again. After the launch, space flight, re-entry into Earth's atmosphere and landing, the so-called plasmid DNA molecules were still found on all the application points on the rocket from the TEXUS-49 mission. And this was not the only surprise: For the most part, the DNA salvaged was even still able to transfer genetic information to bacterial and connective tissue cells. "This study provides experimental evidence that the DNA's genetic information is essentially capable of surviving the extreme conditions of space and the re-entry into Earth's dense atmosphere," says study head Professor Oliver Ullrich from the University of Zurich's Institute of Anatomy.

Spontaneous second mission

The experiment called DARE (DNA atmospheric re-entry experiment) resulted from a spontaneous idea: UZH scientists Dr. Cora Thiel and Professor Ullrich were conducting experiments on the TEXUS-49 mission to study the role of gravity in the regulation of gene expression in human cells using remote-controlled hardware inside the rocket's payload. 

During the mission preparations, they began to wonder whether the outer structure of the rocket might also be suitable for stability tests on so-called biosignatures. "Biosignatures are molecules that can prove the existence of past or present extraterrestrial life," explains Dr. Thiel. And so the two UZH researchers launched a small second mission at the European rocket station Esrange in Kiruna, north of the Arctic Circle.

DNA survives the most extreme conditions

The quickly conceived additional experiment was originally supposed to be a pretest to check the stability of biomarkers during spaceflight and re-entry into the atmosphere. Dr. Thiel did not expect the results it produced: "We were completely surprised to find so much intact and functionally active DNA." The study reveals that genetic information from the DNA can essentially withstand the most extreme conditions.

Various scientists believe that DNA could certainly reach us from outer space as Earth is not insulated: in extraterrestrial material made of dust and meteorites, for instance, around 100 tons of which hits our planet every day.

This extraordinary stability of DNA under space conditions also needs to be factored into the interpretion of results in the search for extraterrestrial life: "The results show that it is by no means unlikely that, despite all the safety precautions, space ships could also carry terrestrial DNA to their landing site. We need to have this under control in the search for extraterrestrial life," points out Ullrich.

Source: University of Zurich

Three touchdowns for Rosetta’s lander

This image from Rosetta’s OSIRIS narrow-angle camera is marked to show the location of the first touchdown point of the Philae lander. It is thought that Philae bounced twice before settling on the surface of Comet 67P/Churyumov-Gerasimenko. The OSIRIS image was taken from a distance of 50 km on 2 September 2014, prior to landing. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

After achieving touchdown on a comet for the first time in history, scientists and engineers are busy analysing this new world and the nature of the landing.

Touchdown was confirmed at ESA's Space Operations Centre in Darmstadt, Germany at 16:03 GMT/17:03 CET on 12 November.

Since then, scientists, flight dynamics specialists and engineers from ESA, the Lander Control Centre in Cologne, Germany, and the Philae Science, Operations and Navigation Centre in Toulouse, France have been studying the first data returned from the lander.

These revealed the astonishing conclusion that the lander did not just touch down on Comet 67P/Churyumov-Gerasimenko once, but three times.

The harpoons did not fire and Philae appeared to be rotating after the first touchdown, which indicated that it had lifted from the surface again. Stephan Ulamec, Philae manager at the DLR German Aerospace Center, reported that it touched the surface at 15:34, 17:25 and 17:32 GMT (comet time -- it takes over 28 minutes for the signal to reach Earth, via Rosetta). The information was provided by several of the scientific instruments, including the ROMAP magnetic field analyser, the MUPUS thermal mapper, and the sensors in the landing gear that were pushed in on the first impact.

The first touchdown was inside the predicted landing ellipse, confirmed using the lander's downwards-looking ROLIS descent camera in combination with the orbiter's OSIRIS images to match features.

But then the lander lifted from the surface again -- for 1 hour 50 minutes. During that time, it travelled about 1 km at a speed of 38 cm/s. It then made a smaller second hop, travelling at about 3 cm/s, and landing in its final resting place seven minutes later.

The touchdown signal generated on first touchdown induced the instruments to 'think' that Philae had landed, triggering the next sequence of experiments. Now those data are being used to interpret the bounces. Preliminary data from the CONSERT experiment suggest that Philae could have travelled closer to the large depression known as Site B, perhaps sitting on its rim. High-resolution orbiter images, some of which are still stored on Rosetta, have yet to confirm the location.

The lander remains unanchored to the surface at an as yet undetermined orientation. The science instruments are running and are delivering images and data, helping the team to learn more about the final landing site.

The descent camera revealed that the surface is covered by dust and debris ranging from millimetre to metre sizes. Meanwhile, Philae's CIVA camera returned a panoramic image that on first impressions suggests the lander is close to a rocky wall, and perhaps has one of its three feet in open space.

After discussions as to whether to activate those science instruments that may cause the position of Philae to shift, MUPUS and APXS have both been deployed.

The primary battery enabling the core science goals of the lander may run out some time in the next 24 hours. As for the secondary battery, charged by solar panels on Philae, with only 1.5 hours of sunlight available to the lander each day, there is an impact on the energy budget to conduct science for a longer period of time. The original landing site offered nearly seven hours of illumination per 12.4 hour comet day.

The next update will be made during a Google Hangout at 13:00 GMT/14:00 CET.

Source: European Space Agency

Touchdown! Rosetta’s Philae probe lands on comet

Still image from animation of Philae separating from Rosetta and descending to the surface of comet 67P/Churyumov-Gerasimenko in November 2014. Credit: ESA/ATG medialab

ESA's Rosetta mission has soft-landed its Philae probe on a comet, the first time in history that such an extraordinary feat has been achieved.

After a tense wait during the seven-hour descent to the surface of Comet 67P/Churyumov-Gerasimenko, the signal confirming the successful touchdown arrived on Earth at 16:03 GMT (17:03 CET).

The confirmation was relayed via the Rosetta orbiter to Earth and picked up simultaneously by ESA's ground station in Malargüe, Argentina and NASA's station in Madrid, Spain. The signal was immediately confirmed at ESA's Space Operations Centre, ESOC, in Darmstadt, and DLR's Lander Control Centre in Cologne, both in Germany.

The first data from the lander's instruments were transmitted to the Philae Science, Operations and Navigation Centre at France's CNES space agency in Toulouse.

"Our ambitious Rosetta mission has secured a place in the history books: not only is it the first to rendezvous with and orbit a comet, but it is now also the first to deliver a lander to a comet's surface," noted Jean-Jacques Dordain, ESA's Director General.

"With Rosetta we are opening a door to the origin of planet Earth and fostering a better understanding of our future. ESA and its Rosetta mission partners have achieved something extraordinary today."

"After more than 10 years travelling through space, we're now making the best ever scientific analysis of one of the oldest remnants of our Solar System," said Alvaro Giménez, ESA's Director of Science and Robotic Exploration.

"Decades of preparation have paved the way for today's success, ensuring that Rosetta continues to be a game-changer in cometary science and space exploration."

"We are extremely relieved to be safely on the surface of the comet, especially given the extra challenges that we faced with the health of the lander," said Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center.

"In the next hours we'll learn exactly where and how we've landed, and we'll start getting as much science as we can from the surface of this fascinating world."

Rosetta was launched on 2 March 2004 and travelled 6.4 billion kilometres through the Solar System before arriving at the comet on 6 August 2014.

"Rosetta's journey has been a continuous operational challenge, requiring an innovative approach, precision and long experience," said Thomas Reiter, ESA Director of Human Spaceflight and Operations.

"This success is testimony to the outstanding teamwork and the unique knowhow in operating spacecraft acquired at the European Space Agency over the decades."

The landing site, named Agilkia and located on the head of the bizarre double-lobed object, was chosen just six weeks after arrival based on images and data collected at distances of 30-100 km from the comet. Those first images soon revealed the comet as a world littered with boulders, towering cliffs and daunting precipices and pits, with jets of gas and dust streaming from the surface.

Following a period spent at 10 km to allow further close-up study of the chosen landing site, Rosetta moved onto a more distant trajectory to prepare for Philae's deployment.

Five critical go/no-go decisions were made last night and early this morning, confirming different stages of readiness ahead of separation, along with a final preseparation manoeuvre by the orbiter.

Deployment was confirmed at 09:03 GMT (10:03 CET) at a distance of 22.5km from the centre of the comet. During the seven-hour descent, which was made without propulsion or guidance, Philae took images and recorded information about the comet's environment.

"One of the greatest uncertainties associated with the delivery of the lander was the position of Rosetta at the time of deployment, which was influenced by the activity of the comet at that specific moment, and which in turn could also have affected the lander's descent trajectory," said Sylvain Lodiot, ESA Rosetta Spacecraft Operations Manager.

"Furthermore, we're performing these operations in an environment that we've only just started learning about, 510 million kilometres from Earth."

Touchdown was planned to take place at a speed of around 1 m/s, with the three-legged landing gear absorbing the impact to prevent rebound, and an ice screw in each foot driving into the surface.

At the same time, two harpoons fired and locked the probe onto the surface.

But during the final health checks of the lander before separation, a problem was detected with the small thruster on top that was designed to counteract the recoil of the harpoons to push the lander down onto the surface. The conditions of landing -- including whether or not the thruster performed -- along with the exact location of Philae on the comet are being analysed.

The first images from the surface are being downlinked to Earth and should be available within a few hours of touchdown.

Over the next 2.5 days, the lander will conduct its primary science mission, assuming that its main battery remains in good health. An extended science phase using the rechargeable secondary battery may be possible, assuming Sun illumination conditions allow and dust settling on the solar panels does not prevent it. This extended phase could last until March 2015, after which conditions inside the lander are expected to be too hot for it to continue operating.

Science highlights from the primary phase will include a full panoramic view of the landing site, including a section in 3D, high-resolution images of the surface immediately underneath the lander, on-the-spot analysis of the composition of the comet's surface materials, and a drill that will take samples from a depth of 23 cm and feed them to an onboard laboratory for analysis.

The lander will also measure the electrical and mechanical characteristics of the surface. In addition, low-frequency radio signals will be beamed between Philae and the orbiter through the nucleus to probe the internal structure.

The detailed surface measurements that Philae makes at its landing site will complement and calibrate the extensive remote observations made by the orbiter covering the whole comet.

"Rosetta is trying to answer the very big questions about the history of our Solar System. What were the conditions like at its infancy and how did it evolve? What role did comets play in this evolution? How do comets work?" said Matt Taylor, ESA Rosetta project scientist.

"Today's successful landing is undoubtedly the cherry on the icing of a 4 km-wide cake, but we're also looking further ahead and onto the next stage of this ground-breaking mission, as we continue to follow the comet around the Sun for 13 months, watching as its activity changes and its surface evolves."

While Philae begins its close-up study of the comet, Rosetta must manoeuvre from its post-separation path back into an orbit around the comet, eventually returning to a 20 km orbit on 6 December.

Next year, as the comet grows more active, Rosetta will need to step further back and fly unbound 'orbits', but dipping in briefly with daring flybys, some of which will bring it within just 8 km of the comet centre.

The comet will reach its closest distance to the Sun on 13 August 2015 at about 185 million km, roughly between the orbits of Earth and Mars. Rosetta will follow it throughout the remainder of 2015, as they head away from the Sun and activity begins to subside.

"It's been an extremely long and hard journey to reach today's once-in-a-lifetime event, but it was absolutely worthwhile. We look forward to the continued success of the great scientific endeavour that is the Rosetta mission as it promises to revolutionise our understanding of comets," said Fred Jansen, ESA Rosetta mission manager.

More about Rosetta

Rosetta is an ESA mission with contributions from its Member States and NASA. Rosetta's Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI. Rosetta is the first mission in history to rendezvous with a comet. It is escorting the comet as they orbit the Sun together, and has deployed a lander to its surface.Comets are time capsules containing primitive material left over from the epoch when the Sun and its planets formed. By studying the gas, dust and structure of the nucleus and organic materials associated with the comet, via both remote and in situ observations, the Rosetta mission should become the key to unlocking the history and evolution of our Solar System.

Source: European Space Agency

Rosetta and Philae separation confirmed

Artist impression showing Philae separating from Rosetta and descending to the surface of comet 67P/Churyumov-Gerasimenko. Credit: Image courtesy of European Space Agency

The Philae lander has separated from the Rosetta orbiter, and is now on its way to becoming the first spacecraft to touch down on a comet.

Separation was confirmed at ESA's Space Operation Centre, ESOC, in Darmstadt, Germany at 09:03 GMT / 10:03 CET. It takes the radio signals from the transmitter on Rosetta 28 minutes and 20 seconds to reach Earth, so separation actually occurred in space at 08:35 GMT / 09:35 CET.

The first signal from Philae is expected in around two hours, when the lander establishes a communication link with Rosetta. Philae cannot send its data to Earth directly -- it must do it via Rosetta.

Once the link has been established, the lander will relay via Rosetta a status report of its health, along with the first science data. This will include images taken of the orbiter shortly after separation.

The descent to the surface of Comet 67P/Churyumov-Gerasimenko will take around seven hours, during which the lander will take measurements of the environment around the comet. It will also take images of the final moments of descent.

Confirmation of a successful touchdown is expected in a one-hour window centred on 16:02 GMT / 17:02 CET. The first image from the surface is expected some two hours later.

Source: European Space Agency

Large coronal hole near the sun's north pole

The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun’s north pole on July 18, 2013, at 9:06 a.m. EDT.
Credit: ESA & NASA/SOHO

The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun's north pole on July 18, 2013, at 9:06 a.m. EDT. Coronal holes are dark, low density regions of the sun's outermost atmosphere, the corona. They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings.

Coronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun's activity cycle. The activity cycle is currently ramping up toward what is known as solar maximum, currently predicted for late 2013. During this portion of the cycle, the number of coronal holes decreases. During solar max, the magnetic fields on the sun reverse and new coronal holes appear near the poles with the opposite magnetic alignment. The coronal holes then increase in size and number, extending further from the poles as the sun moves toward solar minimum again. At such times, coronal holes have appeared that are even larger than this one.

The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere. While it's unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.

Source: NASA/Goddard Space Flight Center

Moon mission: Images of LADEE's impact crater captured

LRO has imaged the LADEE impact site on the eastern rim of Sundman V crater. The image was created by ratioing two images, one taken before the impact and another afterwards. The bright area highlights what has changed between the time of the two images, specifically the impact point and the ejecta. Credit: NASA/Goddard/Arizona State University

NASA'S Lunar Reconnaissance Orbiter (LRO) spacecraft has spied a new crater on the lunar surface; one made from the impact of NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) mission.

"The Lunar Reconnaissance Orbiter Camera (LROC) team recently developed a new computer tool to search Narrow Angle Camera (NAC) before and after image pairs for new craters, the LADEE impact event provided a fun test, said Mark Robinson, LROC principal investigator from Arizona State University in Tempe. "As it turns there were several small surface changes found in the predicted area of the impact, the biggest and most distinctive was within 968 feet (295 meters) of the spot estimated by the LADEE operations team. What fun!"

The LADEE mission ended on April 18, 2014, with the spacecraft's planned impact into the eastern rim of Sundman V crater on the far side of the moon.

LRO has imaged the LADEE impact site on the eastern rim of Sundman V crater. The image was created by ratioing two images, one taken before the impact and another afterwards. 

The bright area highlights what has changed between the time of the two images, specifically the impact point and the ejecta.

LADEE's engines fired April 11, 2014, to perform a final orbital maintenance maneuver and adjust to guarantee it would impact on the farside of the moon and away from the Apollo landing sites. Over a seven-day period, LADEE's orbit decreased and the spacecraft orbited very low to the surface and close to the walls of lunar craters and mountain ridges to give the team a chance to collect valuable science data. Finally, LADEE impacted the eastern rim of Sundman V crater on April 18. The impact site is about half a mile (780 meters) from the crater rim with an altitude of about 8,497 feet (2,590 meters) and was only about two tenths of a mile (300 meters) north of the location mission controllers predicted based on tracking data.

The impact crater is small, less than ten feet (three meters) in diameter, barely resolvable by the LROC NAC. The crater is small because the spacecraft -- compared to most celestial impacts -- was not traveling very fast, approximately 3,800 miles per hour (1,699 meters per second) and had a low mass and a low density. The size of the impact crater made it hard to identify among the myriad of small fresh craters on the lunar surface. Images acquired of the impact region before the impact, were compared with images obtained after the impact to identify the crater.

Since the NAC images are so large (250 mega-pixels) and the new crater is so small, the LROC team co-registered the before and after images (called a temporal pair) and then divided the before image by the after image. By doing this, changes to the surface become evident.

The ejecta from the impact forms a triangular pattern primarily downrange to the west, extending about 656-984 feet (200-300 meters) from the impact site. There is also a small triangular area of ejecta up range but it extends only about 66-98 feet (20-30 meters). The ejecta pattern is oriented northwest, consistent with the direction the spacecraft was traveling when it impacted the surface.

"I'm happy that the LROC team was able to confirm the LADEE impact point," said Butler Hine, LADEE project manager at Ames Research Center in Moffett Field, California. "It really helps the LADEE team to get closure and know exactly where the product of their hard work wound up."

LADEE launched Sept. 6, 2013 from Pad 0B at the Mid-Atlantic Regional Spaceport, at NASA's Wallops Flight Facility, Wallops Island, Virginia. LADEE gathered detailed information about the structure and composition of the thin lunar atmosphere and determining whether dust is being lofted into the lunar sky.

LRO launched September 18, 2009. LRO continues to bring the world astounding views of the lunar surface and a sizable collection of lunar data for research.

LRO recently received a second two-year extended mission. Under the extended mission, LRO will study the seasonal volatile cycle; determine how many small meteorites are currently hitting the moon and their effects; characterize the structure of the lunar regolith; investigate the moon's interaction with the space environment; and reveal more about the lunar interior using observations of the moon's surface.

"With LRO, NASA will study our nearest celestial neighbor for at least two more years," said John Keller, LRO project scientist from NASA's Goddard Space Flight Center in Greenbelt, Maryland. "LRO continues to increase our understanding of the moon and its environment."

Source: nasa

New isotopic evidence supporting moon formation via Earth collision with planet-sized body

The moon. A new series of measurements of oxygen isotopes provides increasing evidence that the moon formed from the collision of the Earth with another large, planet-sized astronomical body, around 4.5 billion years ago. Credit: NASA/JPL

A new series of measurements of oxygen isotopes provides increasing evidence that the Moon formed from the collision of Earth with another large, planet-sized astronomical body, around 4.5 billion years ago.

This work will be published in Science on 6th June, and will be presented to the Goldschmidt geochemistry conference in California on 11th June.

Most planetary scientists believe that the Moon formed from an impact between  Earth and a planet-sized body, which has been given the name Theia. Efforts to confirm that the impact had taken place had centred on measuring the ratios between the isotopes of oxygen, titanium, silicon and others. 

These ratios are known to vary throughout the solar system, but their close similarity between Earth and Moon conflicted with theoretical models of the collision that indicated that the Moon would form mostly from Theia, and thus would be expected to be compositionally different from Earth.

Now a group of German researchers, led by Dr. Daniel Herwartz, have used more refined techniques to compare the ratios of 17O/16O in lunar samples, with those from Earth. The team initially used lunar samples which had arrived on Earth via meteorites, but as these samples had exchanged their isotopes with water from Earth, fresher samples were sought. These were provided by NASA from the Apollo 11, 12 and 16 missions; they were found to contain significantly higher levels of 17O/16O than their Earthly counterparts.

Dr Herwartz said "The differences are small and difficult to detect, but they are there. This means two things; firstly we can now be reasonably sure that the Giant collision took place. Secondly, it gives us an idea of the geochemistry of Theia. Theia seems to have been similar to what we call E-type chondrites.If this is true, we can now predict the geochemical and isotopic composition of the Moon, because the present Moon is a mixture of Theia and the early Earth. The next goal is to find out how much material of Theia is in the Moon."

Most models estimate that the Moon it is composed of around 70% to 90% material from Theia, with the remaining 10% to 30% coming from the early Earth. However, some models argue for as little as 8% Theia in the Moon. Dr Herwartz said that the new data indicate that a 50:50 mixture seems possible, but this needs to be confirmed.

The team used an advanced sample preparation technique before measuring the samples via stable isotope ratio mass spectrometry, which showed a 12 parts per million (± 3 ppm) difference in 17O/16O ratio between Earth and Moon.

Source: European Association of Geochemistry

Making measurements when a comet passes close to Mars

Comet Siding Spring and Mars. Credit: Artist's impression: NASA

On Sunday 19 October at 20:29 CET a comet will pass close to the planet Mars. At the same time the Swedish instrument ASPERA-3 is on board the European satellite Mars Express orbiting Mars and ready to make measurements.

"No one has before made measurements when a comet passes so close by a planet," says Associate Professor Mats Holmström at the Swedish Institute of Space Physics in Kiruna, Sweden.

The comet Siding Spring will pass by Mars at a distance of only 140,000 km, about a third of the distance from the Earth to the Moon, by way of comparison. The outer parts of the comet's thin atmosphere will collide at high speed (56 km/sec) with the atmosphere of Mars.

"We expect that gas and dust from the comet will impact on the Martian atmosphere, which will be temporarily heated and will expand," says Mats Holmström. "We should be able to see that with our instrument."

The Swedish Institute of Space Physics (IRF) has Principal Investigator responsibility for the satellite instrument ASPERA-3 which is an international collaboration with participants from some 15 research groups from about 10 countries. ASPERA-3 on board the measures how charged particles from the sun, the so-called solar wind, influences the atmosphere of Mars. Mars Express was lauched by the European Space Agency (ESA) and has been orbiting Mars since 2003.

Source: Expertsvar

Water vapor on Rosetta's target comet significantly different from that found on Earth

First measurements of comet’s water ratio. Credit: Copyright Spacecraft: ESA/ATG medialab; Comet: ESA/Rosetta/NavCam; Data: Altwegg et al. 2014

ESA's Rosetta spacecraft has found the water vapour from its target comet to be significantly different to that found on Earth. The discovery fuels the debate on the origin of our planet's oceans.

The measurements were made in the month following the spacecraft's arrival at Comet 67P/Churyumov-Gerasimenko on 6 August. It is one of the most anticipated early results of the mission, because the origin of Earth's water is still an open question.

One of the leading hypotheses on Earth's formation is that it was so hot when it formed 4.6 billion years ago that any original water content should have boiled off. But, today, two thirds of the surface is covered in water, so where did it come from?
In this scenario, it should have been delivered after our planet had cooled down, most likely from collisions with comets and asteroids. The relative contribution of each class of object to our planet's water supply is, however, still debated.

The key to determining where the water originated is in its 'flavour', in this case the proportion of deuterium -- a form of hydrogen with an additional neutron -- to normal hydrogen.

This proportion is an important indicator of the formation and early evolution of the Solar System, with theoretical simulations showing that it should change with distance from the Sun and with time in the first few million years.

One key goal is to compare the value for different kinds of object with that measured for Earth's oceans, in order to determine how much each type of object may have contributed to Earth's water.

Comets in particular are unique tools for probing the early Solar System: they harbour material left over from the protoplanetary disc out of which the planets formed, and therefore should reflect the primordial composition of their places of origin.

But thanks to the dynamics of the early Solar System, this is not a straightforward process. Long-period comets that hail from the distant Oort cloud originally formed in Uranus-Neptune region, far enough from the Sun that water ice could survive.

They were later scattered to the Solar System's far outer reaches as a result of gravitational interactions with the gas giant planets as they settled in their orbits.

Conversely, Jupiter-family comets like Rosetta's comet were thought to have formed further out, in the Kuiper Belt beyond Neptune. Occasionally these bodies are disrupted from this location and sent towards the inner Solar System, where their orbits become controlled by the gravitational influence of Jupiter.

Indeed, Rosetta's comet now travels around the Sun between the orbits of Earth and Mars at its closest and just beyond Jupiter at its furthest, with a period of about 6.5 years.

Previous measurements of the deuterium/hydrogen (D/H) ratio in other comets have shown a wide range of values. Of the 11 comets for which measurements have been made, it is only the Jupiter-family Comet 103P/Hartley 2 that was found to match the composition of Earth's water, in observations made by ESA's Herschel mission in 2011.

By contrast, meteorites originally hailing from asteroids in the Asteroid Belt also match the composition of Earth's water. Thus, despite the fact that asteroids have a much lower overall water content, impacts by a large number of them could still have resulted in Earth's oceans.

It is against this backdrop that Rosetta's investigations are important. Interestingly, the D/H ratio measured by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, or ROSINA, is more than three times greater than for Earth's oceans and for its Jupiter-family companion, Comet Hartley 2. Indeed, it is even higher than measured for any Oort cloud comet as well.

"This surprising finding could indicate a diverse origin for the Jupiter-family comets -- perhaps they formed over a wider range of distances in the young Solar System than we previously thought," says Kathrin Altwegg, principal investigator for ROSINA and lead author of the paper reporting the results in the journal Science this week.

"Our finding also rules out the idea that Jupiter-family comets contain solely Earth ocean-like water, and adds weight to models that place more emphasis on asteroids as the main delivery mechanism for Earth's oceans."

"We knew that Rosetta's in situ analysis of this comet was always going to throw up surprises for the bigger picture of Solar System science, and this outstanding observation certainly adds fuel to the debate about the origin of Earth's water," says Matt Taylor, ESA's Rosetta project scientist.

"As Rosetta continues to follow the comet on its orbit around the Sun throughout next year, we'll be keeping a close watch on how it evolves and behaves, which will give us unique insight into the mysterious world of comets and their contribution to our understanding of the evolution of the Solar System."

Source: ESA

Artist impression of the debris disc and planets around the star known as Gliese 581, superimposed on Herschel PACS images at 70, 100 and 160 micrometre wavelengths. The line drawing superimposed on the Herschel image gives a schematic representation of the location and orientation of the star, planets and disc, albeit not to scale. Credit: Image courtesy of European Space Agency (ESA)

Using ESA's Herschel space observatory, astronomers have discovered vast comet belts surrounding two nearby planetary systems known to host only Earth-to-Neptune-mass worlds. The comet reservoirs could have delivered life-giving oceans to the innermost planets.

In a previous Herschel study, scientists found that the dusty belt surrounding nearby star Fomalhaut must be maintained by collisions between comets.

In the new Herschel study, two more nearby planetary systems -- GJ 581 and 61 Vir -- have been found to host vast amounts of cometary debris.

Herschel detected the signatures of cold dust at 200ºC below freezing, in quantities that mean these systems must have at least 10 times more comets than in our own Solar System's Kuiper Belt.

GJ 581, or Gliese 581, is a low-mass M dwarf star, the most common type of star in the Galaxy. Earlier studies have shown that it hosts at least four planets, including one that resides in the 'Goldilocks Zone' -- the distance from the central sun where liquid surface water could exist.

Two planets are confirmed around G-type star 61 Vir, which is just a little less massive than our Sun.

The planets in both systems are known as 'super-Earths', covering a range of masses between 2 and 18 times that of Earth.

Interestingly, however, there is no evidence for giant Jupiter- or Saturn-mass planets in either system.

The gravitational interplay between Jupiter and Saturn in our own Solar System is thought to have been responsible for disrupting a once highly populated Kuiper Belt, sending a deluge of comets towards the inner planets in a cataclysmic event that lasted several million years.

"The new observations are giving us a clue: they're saying that in the Solar System we have giant planets and a relatively sparse Kuiper Belt, but systems with only low-mass planets often have much denser Kuiper belts," says Dr Mark Wyatt from the University of Cambridge, lead author of the paper focusing on the debris disc around 61 Vir.

"We think that may be because the absence of a Jupiter in the low-mass planet systems allows them to avoid a dramatic heavy bombardment event, and instead experience a gradual rain of comets over billions of years."

"For an older star like GJ 581, which is at least two billion years old, enough time has elapsed for such a gradual rain of comets to deliver a sizable amount of water to the innermost planets, which is of particular importance for the planet residing in the star's habitable zone," adds Dr Jean-Francois Lestrade of the Observatoire de Paris who led the work on GJ 581.

However, in order to produce the vast amount of dust seen by Herschel, collisions between the comets are needed, which could be triggered by a Neptune-sized planet residing close to the disc.

"Simulations show us that the known close-in planets in each of these systems cannot do the job, but a similarly-sized planet located much further from the star -- currently beyond the reach of current detection campaigns -- would be able to stir the disc to make it dusty and observable," says Dr Lestrade.

"Herschel is finding a correlation between the presence of massive debris discs and planetary systems with no Jupiter-class planets, which offers a clue to our understanding of how planetary systems form and evolve," says Göran Pilbratt, ESA's Herschel project scientist.

Source: European Space Agency (ESA)

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

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

Sun sizzles in high-energy X-rays

X-rays stream off the sun in this image showing observations from by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, overlaid on a picture taken by NASA's Solar Dynamics Observatory (SDO).
Credit: NASA/JPL-Caltech/GSFC

For the first time, a mission designed to set its eyes on black holes and other objects far from our solar system has turned its gaze back closer to home, capturing images of our sun. NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has taken its first picture of the sun, producing the most sensitive solar portrait ever taken in high-energy X-rays.

NuSTAR will give us a unique look at the sun, from the deepest to the highest parts of its atmosphere," said David Smith, a solar physicist and member of the NuSTAR team at University of California, Santa Cruz.

Solar scientists first thought of using NuSTAR to study the sun about seven years ago, after the space telescope's design and construction was already underway (the telescope launched into space in 2012). Smith had contacted the principal investigator, Fiona Harrison of the California Institute of Technology in Pasadena, who mulled it over and became excited by the idea.

"At first I thought the whole idea was crazy," says Harrison. "Why would we have the most sensitive high energy X-ray telescope ever built, designed to peer deep into the universe, look at something in our own back yard?" Smith eventually convinced Harrison, explaining that faint X-ray flashes predicted by theorists could only be seen by NuSTAR.

While the sun is too bright for other telescopes such as NASA's Chandra X-ray Observatory, NuSTAR can safely look at it without the risk of damaging its detectors. The sun is not as bright in the higher-energy X-rays detected by NuSTAR, a factor that depends on the temperature of the sun's atmosphere.
This first solar image from NuSTAR demonstrates that the telescope can in fact gather data about sun. And it gives insight into questions about the remarkably high temperatures that are found above sunspots -- cool, dark patches on the sun. Future images will provide even better data as the sun winds down in its solar cycle.

"We will come into our own when the sun gets quiet," said Smith, explaining that the sun's activity will dwindle over the next few years.

With NuSTAR's high-energy views, it has the potential to capture hypothesized nanoflares -- smaller versions of the sun's giant flares that erupt with charged particles and high-energy radiation. Nanoflares, should they exist, may explain why the sun's outer atmosphere, called the corona, is sizzling hot, a mystery called the "coronal heating problem." The corona is, on average, 1.8 million degrees Fahrenheit (1 million degrees Celsius), while the surface of the sun is relatively cooler at 10,800 Fahrenheit (6,000 degrees Celsius). It is like a flame coming out of an ice cube. Nanoflares, in combination with flares, may be sources of the intense heat.

If NuSTAR can catch nanoflares in action, it may help solve this decades-old puzzle.

"NuSTAR will be exquisitely sensitive to the faintest X-ray activity happening in the solar atmosphere, and that includes possible nanoflares," said Smith.
What's more, the X-ray observatory can search for hypothesized dark matter particles called axions. Dark matter is five times more abundant than regular matter in the universe. Everyday matter familiar to us, for example in tables and chairs, planets and stars, is only a sliver of what's out there. While dark matter has been indirectly detected through its gravitational pull, its composition remains unknown.

It's a long shot, say scientists, but NuSTAR may be able spot axions, one of the leading candidates for dark matter, should they exist. The axions would appear as a spot of X-rays in the center of the sun.

Meanwhile, as the sun awaits future NuSTAR observations, the telescope is continuing with its galactic pursuits, probing black holes, supernova remnants and other extreme objects beyond our solar system.

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Virginia. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley; Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Maryland; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, California; ATK Aerospace Systems, Goleta, California; and with support from the Italian Space Agency (ASI) Science Data Center.

NuSTAR's mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, California. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

Source: NASA