Posted on by Jason Major

Kepler Team Announces New Rocky Planet

Artist's impression of Kepler-10c (foreground planet)

 

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Today at the American Astronomical Society conference in Boston, the Kepler team announced the confirmation of a new rocky planet in orbit around Kepler-10. Dubbed Kepler-10c, this planet is described as a “scorched, molten Earth.”

2.2 times the radius of Earth, Kepler-10c orbits its star every 45 days. Both it and its smaller, previously-discovered sibling 10b are located too close to their star for liquid water to exist.

Kepler-10c was validated using a new computer simulation technique called “Blender” as well as additional infrared data from NASA’s Spitzer Space Telescope. This method can be used to locate Earth-sized planets within Kepler’s field of view and could also potentially help find Earth-sized planets within other stars’ habitable zones.

This is the first time the team feels sure that it has exhaustively ruled out alternative explanations for dips in the brightness of a star… basically, they are 99.998% sure that Kepler-10c exists.

The Kepler-10 star system is located about 560 light-years away near the Cygnus and Lyra constellations.

Read the release on the Nature.com blog.

Image credit: NASA/Ames/JPL-Caltech

Posted on by Jason Major

Messages from Mercury

MESSENGER's view from Mercury's south pole

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It’s been just over two months since the MESSENGER spacecraft successfully entered orbit around Mercury, back on March 18, and it’s been enthusiastically returning image after image of our solar system’s innermost planet at a unprecedented rate. Which, of course, is just fine with us!

The image above shows Mercury’s southern hemisphere and the bright rays of the 50-km-wide crater Han Kan. It was acquired on May 17, 2011.

Below are more recent images from MESSENGER… some of which show regions and features that have never previously been mapped – or even named!

Unnamed double peak-ring basin. Acquired May 13.
Detail of the mountains that make up the rim of Caloris Basin. Acquired May 5.
Narrow-angle camera view of the 100-km-wide Atget crater. Acquired May 10.
Color map of Mercury's surface. The bright crater is Snorri (21km wide). Acquired April 15.

Click on the images to see more detail on the MESSENGER mission site.

MESSENGER’s orbit about Mercury is highly elliptical, taking it 200 kilometers (124 miles) above its northern surface at the closest pass and 15,193 kilometers (9,420 miles) away from the south pole at furthest. Check out this video showing an animation of how a typical MESSENGER orbit would be executed.

Image credits: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft’s seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System’s innermost planet. During the one-year primary mission, MDIS is scheduled to acquire more than 75,000 images in support of MESSENGER’s science goals.

Posted on by Jason Major

Lone Planets “More Common Than Stars”

Artist's concept of a free-floating Jupiter-like planet. (NASA / JPL-Caltech)

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We happen to live in a solar system where everything seems to be tucked neatly in place. Sun, planets, moons, asteroids, comets… all turning and traveling through space in relatively neat and orderly fashions. But that may not always be the case; sometimes planets can get kicked out of their solar systems entirely, banished to roam interstellar space without a sun of their own. And these “orphan planets” may be much more numerous than once thought.

Researchers in a joint Japan-New Zealand study surveyed microlensing events near the central part of our galaxy during 2006 and 2007 and identified up to 10 Jupiter-sized orphan worlds between 10,000 and 20,000 light-years away. Based on the number of planets identified and the area studied they estimate that there could literally be hundreds of billions of these lone planets roaming our galaxy….literally twice as many planets as there are stars.

“Although free-floating planets have been predicted, they finally have been detected, holding major implications for planetary formation and evolution models.”

– Mario Perez, exoplanet program scientist at NASA Headquarters in Washington.

From the NASA release:

Previous observations spotted a handful of free-floating, planet-like objects within star-forming clusters, with masses three times that of Jupiter. But scientists suspect the gaseous bodies form more like stars than planets. These small, dim orbs, called brown dwarfs, grow from collapsing balls of gas and dust, but lack the mass to ignite their nuclear fuel and shine with starlight. It is thought the smallest brown dwarfs are approximately the size of large planets.

On the other hand, it is likely that some planets are ejected from their early, turbulent solar systems, due to close gravitational encounters with other planets or stars. Without a star to circle, these planets would move through the galaxy as our sun and other stars do, in stable orbits around the galaxy’s center. The discovery of 10 free-floating Jupiters supports the ejection scenario, though it’s possible both mechanisms are at play.

“If free-floating planets formed like stars, then we would have expected to see only one or two of them in our survey instead of 10. Our results suggest that planetary systems often become unstable, with planets being kicked out from their places of birth.”

– David Bennett, a NASA and National Science Foundation-funded co-author of the study from the University of Notre Dame.

The study wasn’t able to resolve planets smaller than Saturn but it’s believed there are likely many more smaller, Earth-sized worlds than large Jupiter-sized ones.

Read the full NASA news release here.

The study, led by Takahiro Sumi from Osaka University in Japan, appears in the May 19 issue of the journal Nature.

Posted on by Nancy Atkinson

Guest Post: Drifting on Alien Winds: Exploring the Skies and Weather of Other Worlds

Triton Probe: Neptune’s blue skies may be visited by beachball-sized methane raindrops. (painting ©Michael Carroll)

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Editor’s note: We all want to explore other worlds in our solar system, but perhaps you haven’t considered the bizarre weather you’d encounter — from the blistering hurricane-force winds of Venus to the gentle methane rain showers of Saturn’s giant moon Titan. Science journalist Michael Carroll has written a guest post for Universe Today which provides peek at the subject matter for his new book, “Drifting on Alien Winds: Exploring the Skies and Weather of Other Worlds.”

It’s been a dramatic year for weather on Earth. Blizzards have blanketed the east coast, crippling traffic and power grids. Cyclone Tasha drenched Queensland, Australia as rainfall swelled the mighty Mississippi, flooding the southern US. Eastern Europe and Asia broke high temperature records. But despite these meteorological theatrics, the Earth’s conditions are a calm echo of the weather on other worlds in our solar system.


Take our nearest planetary neighbor, Venus. Nearly a twin of Earth in size, Venus displays truly alien weather. The hurricane-force Venusian winds are ruled not by water (as on Earth), but by battery acid. Sunlight tears carbon dioxide molecules (CO2) apart in a process called photodissociation. Leftover bits of molecules frantically try to combine with sulfur and water to become chemically stable, resulting acid hazes. Temperatures soar to 900ºF at the surface, where air is as dense as the Earthly oceans at a depth of X feet.

Venus is the poster child of comparative planetology, the study of other planets to help us understand our own. Earth’s simmering sibling has taught us about greenhouse gases, and gave us an even more immediate cautionary tale in 1978. The Pioneer Venus orbiter discovered that Venus naturally generates chlorofluorocarbons (CFCs) in its atmosphere. These CFCs were tearing holes in the planet’s ozone. At the same time, a wide variety of industries were preparing to use CFCs in insecticides, spray paints, and other aerosol products. Venus presented us with a warning that may have averted a planet-wide crisis.

In the same way, Mars has provided insights into long-term climate change. Its weather is a simplified version of our own. Locked within its rocks and polar caps lie records of changing climate over eons.

Jupiter’s Great Red Spot is a cyclone larger than two Earths. (photomontage ©Michael Carroll)

But fans of really extreme weather must venture further out, to the outer planets. Jupiter and Saturn are giant balls of gas with no solid surface, and are known as the “gas giants.” They are truly gigantic: over a thousand Earths could fit within Jupiter itself.

The skies of Jupiter and Saturn are dominated by hydrogen and helium, the ancient building blocks of the solar system. Ammonia mixes in to produce a rich brew of complex chemistry, painting the clouds of Jupiter and Saturn in tans and grays. Lightning bolts sizzle through the clouds, powerful enough to electrify a small city for weeks. Ammonia forms rain and snow in the frigid skies. Jupiter’s Great Red Spot is a centuries-old cyclone large enough to swallow three Earths. Saturn has its own bizarre storms: a vast hexagon-shaped trough of clouds races across the northern hemisphere. Over the south pole, a vast whirlpool gazes from concentric clouds like a Cyclops.

Clouds tower into a twilight sky on Saturn. The planet’s glowing rings seem to bend at the horizon because of the dense air. (painting ©Michael Carroll)

Beyond Jupiter and Saturn lie the “ice giants”, Uranus and Neptune. These behemoths host atmospheres of poisonous brews chilled to cryogenic temperatures. Methane tints Uranus and Neptune blue. Neptune’s clear air reveals a teal cloud deck. Hydrocarbon hazes tinge Uranus to a paler shade of blue-green. Neptune’s clear air is somewhat of a mystery to scientists. This may be because cloud-forming particles can’t stay airborne long enough to become visible clouds. Some scientists propose that Neptune’s abundant methane rains may condense so rapidly that within a few seconds tiny methane raindrops swell to something the size of a beachball. There are no clouds adrift, because methane rains out of the atmosphere too quickly.

One of the strangest cases of bizarre weather comes to us from Neptune’s moon Triton. Triton’s meager nitrogen air is tied to the freezing and thawing of polar ices, also composed of nitrogen. Triton’s entire atmosphere collapses twice a year, when it’s winter on one of the poles. At that time of year, all of Triton’s air migrates to the winter pole, where it freezes to the ground. The moon only has “weather” during the spring and fall; its atmosphere exists only during those seasons.

So, the next time you contemplate complaining about the heat, think of Venus. And if it’s blizzards you worry about, find comfort in Triton: at least our atmosphere doesn’t disappear in winter!

For more on the subject, see Michael Carroll’s newest book, Drifting on Alien Winds: Exploring the Skies and Weather of Other Worlds from Springer.

Posted on by VirtualAstro

Dawn Planetary Delights

Dawn 11th May Credit: Adrian West

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During the month of May, four bright Planets will grace the morning sky just before dawn.

The planets Venus, Jupiter, Mercury and Mars will be involved in a series of conjunctions (close together) and will finally be joined by the thin crescent moon at the end of the month.

Twice during May some of the planets will converge to form a trio, where 3 planets will fit in an imaginary circle roughly 5 degrees across.

On the 11th Mercury, Venus and Jupiter will be within 2.5 degrees of each other, forming a very tight trio and on the 21st another trio will be formed by Mercury, Venus and Mars.

Dawn Planets 21st May Credit: Adrian West

On the 29th, 30th, and 31st, the waning crescent moon will arrive, moving past Jupiter, Mars, Venus and Mercury stretched out in a line across the eastern sky.

Dawn 29th May. Credit: Adrian West

Unfortunately, these gatherings will be a challenge especially for observers in high latitudes, as the ecliptic in May is very shallow and low to the horizon. But if all you need is a challenge to get you out observing, then here’s your chance!

Venus and Jupiter should be easy objects to see, but Mercury and Mars will be very difficult, along with the crescent moon due to the onset of daylight.

Be careful as you will be viewing objects close to the sun. Never ever look at the sun with the naked eye, binoculars or a telescope as this will permanently damage your eyes or blind you. Viewing the sun can only be done with specialist solar telescopes and equipment.

Posted on by Nancy Atkinson

Clyde Tombaugh’s Ten Special Commandments for Planet Hunters

The Ten Special Commandments for a Would-Be Planet Hunter, according to Clyde Tombaugh. Scan courtesy of Toney Burkhart.

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Back in 1989, amateur astronomer Toney Burkhart found out that Clyde Tombaugh was going to be giving a talk in San Francisco, just a short distance from Burkhart’s home. Trouble was, he found out only about 10 minutes before the presentation was going to start, so he rushed over and arrived just in time to hear Tombaugh’s talk, where he told amusing stories of how he found Pluto, and what he went through with night after night in a cold observatory taking photographs and comparing the glass plates, looking for a planet in the outer solar system. Then Tombaugh shared read his version of the Ten Commandments, called, “Ten Special Commandments for a Would-Be Planet Hunter.”


Afterward, the posters of the Commandments were being sold as a fund raising event.

“Clyde was going around the country to raise money for scholarships for young people to study planetary science,” Burkhart told Universe Today. “There were a lot of people there in the lobby buying posters autographed by Clyde Tombaugh and I wanted one very much.”

However, when Burkhart went to purchase one, he discovered that in his haste to leave his home, he had forgotten his billfold.

“I waited until everything was over and thought that I would at least go over and say hi to Clyde and tell him how much I thought of his hard work and to shake his hand, at least,” Burkhart said, and Tombaugh was more than happy to chat with an fellow astronomy enthusiast.

“While I was chatting with Clyde, I told him that I wish I brought money to buy one of the posters. He looked at me and smiled and said, ‘Well, that’s alright.’” And I said no, I really would have bought one if I had not ran out of the house and forgot my billfold. He was holding his notes and I asked him, what are you going to do with those notes, throw them away?”

Burkhart said Tombaugh smiled and replied that he couldn’t give away his notes, as he had more talks to give, but said he could mail them to Burkhart after his tour was over.

Burkhart offered to send Tombaugh a check later, or at least pay for postage, but Tombaugh looked at him and said, “No, that’s OK, I see you are really into astronomy and it would be my pleasure to give it you.”

Grateful, Burkhart asked if Tombaugh could autograph it, not for Burkhart but for his son Jason. Tombaugh took Burkhart’s address, and true to his word, about a month later Burkhart received Tombaugh’s personal version of the Commandments, with corrections made in pen, (the corrections were made by Tombaugh’s wife, Patricia, Burkhart said) along with his autograph. “I have them in safekeeping to leave to my son to have and hopefully give them to his kids,” Burkhart said.

Here are the the Ten Special Commandments for a Would-Be Planet Hunter, according to Clyde Tombaugh

1. Behold the heavens and the great vastness thereof, for a planet could be anywhere therein.

2. Thou shalt dedicate thy whole being to the search project with infinite patience and perseverance.

3. Though shalt set no other work before thee for the search shall keep thee busy enough.

4. Though shalt take the plates at opposition time lest thou be deceived by asteroids near their stationary positions.

5. Though shalt duplicate the plate of a pair at the same hour angle lest refraction distortions overtake thee.

6. Thou shalt give adequate overlap of adjacent plate regions lest the planet play hide and seek with thee.

7. Thou must not become ill in the dark of the moon lest thou fall behind the opposition point.

8. Thou shalt have no dates except at full moon when long exposure plates cannot be taken at the telescope.

9. Many false planets shall appear before thee, hundreds of them, and thou shalt check every one with a third plate.

10. Thou shalt not engage in any dissipation, that thy years may be many for thou shalt need them to finish the job!

Clyde W. Tombaugh
14 March 1989

Burkhart shared the scan of Tombaugh’s notes on his Facebook page.

h/t to Charles Bell.

Posted on by Anne Minard

New Studies: Planetary Rings Harbor Records of Past Smash-Ups

Saturn, imaged by Cassini on approach. Credit: CICLOPS

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Planetary rings are more than just astronomical marvels — they’re also a sort of archive, chronicling histories of impacts for decades.

A pair of studies were published online in Science today by two different teams that noticed odd characteristics in the rings of Saturn and Jupiter — and followed them to this promising conclusion. In the first, lead author Mark Showalter of the SETI Institute in Mountain View, Calif. and his team analyzed images of Jupiter’s rings observed in 1996 and 2000 by Galileo, and again in 2007 by Horizon, zeroing in on a pattern they labeled “corrugated,” like a tin roof. Around the same time, Matthew Hedman, from Cornell University in Ithaca, NY and his colleagues discovered similar ripple patterns in the rings of Saturn, from images taken by the Cassini spacecraft.

Image courtesy of Science/AAAS

The images above show how a vertical corrugation can be produced from an initially inclined ring. The top image shows a simple inclined ring (the central planet is omitted for clarity), while the lower two images show the same ring at two later times, where the ring particles’ wobbling orbits have sheared this inclined sheet into an increasingly tightly-wound spiral corrugation.

Carolyn Porco, a co-author on the Hedman-led study and director of the Cassini Imaging Central Laboratory for Operatons (CICLOPS), wrote in an email accompanying the release of the studies that “it has been known for some time that the solar system is filled with debris:  small rocky bits in the inner solar system and icy bits in the
outer solar system that routinely rain down on the planets and their rings and moons.  A couple hundred tons of such debris hits the Earth alone every day. Well, the origins of the spiral ripples in both ring systems have now been pinpointed to very recent impacts between clouds of cometary fragments and the rings.”

Showalter’s team describes a pair of superimposed ripple patterns that showed up in Galileo images in 1996 and again in 2000.

“These patterns behave as two independent spirals, each winding up at a rate defined by Jupiter’s gravity field,” they write. “The dominant pattern originated between July and October 1994, when the entire ring was tilted by ~2 km. We associate this with the ShoemakerLevy 9 impacts of July 1994. New Horizons images still show this pattern 13 years later and suggest that subsequent events may also have tilted the ring.”

Corrugation in Saturn's D-ring. Credit: NASA

Hedman and his team note that rippling had previously been observed in Saturn’s D ring; NASA released the above graphic to explain the phenomenon in 2006. “The C-ring corrugation seems to have been similarly generated, and indeed it was probably created by the same ring-tilting event that produced the D-ring’s corrugation,” they write.

That paper also compares the rate of impacts likely to visit each planet: “… Saturn should encounter debris clouds derived from comets disrupted by previous planetary encounters at a rate that is roughly 0.2 percent of Jupiter’s impact rate.”

They reason that if Jupiter sees impacts from 1-km-wide objects as often as once a decade, “the clouds of orbiting debris created by the disruption of a 1-km-wide comet should rain down on Saturn’s rings once every 5,000-10,000 years. The probability that debris from a previously disrupted comet would hit Saturn’s rings in the last 30 years would then be between roughly 1 percent and 0.1 percent, which is not very small. Such scenarios therefore provide a reasonable explanation for the origin of the observed corrugation in Saturn’s C ring.”

Taken together, the papers show that Saturn’s ring ripples were likely generated by a comet collision in 1983, while Jupiter’s ring ripples occurred after the impact of a comet the summer of 1994 — specifically, the impact of Comet Shoemaker-Levy 9 that left scars on Jupiter still visible today.

Showalter and his coauthors point out that impacts by comets and/or their dust clouds are common occurrences in planetary rings.

“On at least three occasions over the last few decades, these collisions have carried sufficient momentum to tilt a ring of Jupiter or Saturn off its axis by an observable distance. Once such a tilt is established, it can persist for decades, with the passage of time recorded in its ever-tightening spiral,” they write. “Within these subtle patterns, planetary rings chronicle their own battered histories.”

Both papers appear today at the Science Express website. See also the CICLOPS site.

Posted on by Anne Minard

Probing the Moho Boundary – Earth’s Own Unexplored Frontier

Chikyu. Credit: JAMSTEC-CDEX

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JOIDES Resolution. Credit: IODP

The boundary where Earth’s crust gives way to the unexplored mantle was first detected in 1909, because of a change in the travel of seismic waves. Named the Moho boundary for Andrija Mohorovicic, who listened to those seismic waves, the crust-mantle boundary is a frontier that remains elusive and compelling — harboring tantalizing clues as to the story of Earth’s formation — even as our technologies push into the outer reaches of the solar system and beyond.

The first serious attempts to probe the Moho boundary ran aground in the late 1950s. Now, technology already in use on a Japanese ship, combined with a United States digging program already under way, could finally yield success. Damon Teagle and Benoît Ildefonse have written about the ongoing efforts for an article in the journal Nature, released today.

Teagle is at the University of Southampton’s National Oceanography Centre in the UK, and Ildefonse is at Université Montpellier in France. They are co-chief scientists on an expedition called the IODP Expedition 335, “to obtain for the first time a section of the lower oceanic crust — the material lying just above the mantle,” they write.

The IODP is using the U.S. ship JOIDES Resolution, pictured above, which will drill from April to June this year off the coast of Costa Rica.

“This site is in ocean crust that formed superfast — at more than 20 centimetres a year, much faster than any present day crust formation,” the co-authors write. “That makes the upper crust there much thinner than elsewhere, so it is possible to reach the lower portions without having to drill very deep. Three previous expeditions to Hole 1256D have drilled down to more than 1.5 kilometres below the sea floor, into the transition zone between dikes and gabbros.”

This spring they hope to push it another 400 meters, and recover gabbros from the lower crust, “which will be the deepest types of rock ever extracted from beneath the sea floor,” even though the deepest hole reached 2,111 meters under the eastern Pacific off of Colombia, they write.

Microphotograph of a mantle xenolith, sampled on Rapa Island in French Polynesia. The colourful minerals (seen here under the microscope in cross-polarized light, each grain is about 1 to 5mm large) are olivine, the main constituent of the upper mantle. Credit : Andréa Tommasi (CNRS, Géosciences Montpellier)

Teagle and Ildefonse note that some pieces of the mantle have been thrust up to Earth’s surface during tectonic mountain building, and ejected from volcanoes and sea floor dikes. Those samples have provided clues to the mantle’s composition, but they don’t reveal the variability of the mantle — and all of the samples have been altered by the processes that revealed them.

They say the IODP mission should help to settle many debates, including how crust is formed at mid-ocean ridges, how magma from the mantle is intruded into the lower crust, the geometry and vigor of how sea water can pull heat from the lower oceanic crust and the contribution of the lower crust to marine magnetic anomalies. The project will also provide “further impetus for, and confidence in, deep ocean crust drilling,” write Teagle and Ildefonse — but it will reach a depth far less than what will be needed to actually get at the Moho boundary. It occurs at least 30 kilometers (18 miles) under the continents but just 6 kilometers (3.7 miles) under the seas.

That’s where Chikyu comes in. Launched in 2002, “Chikyu is a giant ship, capable of carrying 10 kilometres of drilling pipes, and is equipped for riser drilling in 2.5 kilometres of water,” the authors write. Although Chikyu wouldn’t yet be able to go the full distance, its design is advanced enough to be the launching pad for such efforts:

“The vessel has a riser system: an outer pipe surrounds the drill string — the steel pipe through which cores are recovered,” the co-authors write. “The drilling mud and cuttings are returned up to the vessel in the space between the two pipes. This helps to recycle the drilling mud, control its physical properties and the pressure within the drill hole and helps to stabilize the borehole walls.”

Teagle and Ildefonse say the ideal drilling program to reach the mantle boundary will happen in one of three places — off the coasts of Hawaii, Baja California and Costa Rica — where the water is the most shallow, over the coldest possible crust. Wherever and however it happens, they write, it will be worth doing:

“Drilling to the mantle is the most challenging endeavour in the history of Earth science. It will provide a legacy of fundamental scientific knowledge, and inspiration and training for the next generation of geoscientists, engineers and technologists.”

Source: Nature. See also the websites for Chikyu and JOIDES.

Posted on by Nancy Atkinson

New Horizons Flies by Uranus

An 'overhead' view of New Horizons' location. Credit: NASA

The Pluto-bound New Horizons spacecraft will fly by another planet today (March 18, 2011). However, the robotic craft won’t be taking any images as it zooms past Uranus’ orbit at about 6 p.m. EDT, 3.8 billion kilometers (2.4 billion miles) away from the gas giant (and 2.0 billion km (1.8 billion miles) from Earth). New Horizons is currently in hibernation mode, and the great distance from Uranus means any observations wouldn’t provide much as far as data and images. But, even so, this event is a ‘landmark’ so to speak in New Horizon’s gauntlet across the solar system.

“New Horizons is all about delayed gratification, and our 9 1/2-year cruise to the Pluto system illustrates that,” said Principal Investigator Alan Stern, of the Southwest Research Institute. “Crossing the orbit of Uranus is another milepost along our long journey to the very frontier of exploration.”

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New Horizons is now well over halfway through its journey to Pluto. Motoring along at 57,900 km/hr (36,000 mph), it will travel more than 4.8 billion km (3 billion miles) to fly past Pluto and its moons Nix, Hydra and Charon in July 2015.

But the journey doesn’t end there. After that, New Horizons will head off to a post-Pluto encounter with other objects within the Kuiper Belt, some event(s) which might take place even into the 2020’s. The planetary science community is working on the selection of potential targets.

The mission still has more than 4 years to go to get to Pluto; it will take 9 nine months to send all the data back to Earth.

The next planetary milestone for New Horizons will be the orbit of Neptune, which it crosses on Aug. 25, 2014, exactly 25 years after Voyager 2 made its historic exploration of that giant planet.

“This mission is a marathon,” says Project Manager Glen Fountain, of the Johns Hopkins University Applied Physics Laboratory. “The New Horizons team has been focused on keeping the spacecraft on course and preparing for Pluto. So far, so good, and we are working to keep it that way.”

Source: New Horizons

Posted on by Anne Minard

Did Mars’ Missing Carbon Go Underground in a Wetter Age?

Image credit: NASA/JPL-Caltech/Arizona State Univ. North is toward the top of the image, which is centered at 14 degrees south latitude, 304.4 degrees west longitude.

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A close look at the Wisconsin-sized Huygens Crater, above, in Mars’ southern highlands gave NASA and Arizona State University scientists some clues to announce this week as to a possible source of the carbon that’s mysteriously missing from the red planet’s thin atmosphere.

It might be buried underground.

The impact that formed the crater lifted material from far underground and piled some of it at the crater’s rim, where, at about 10 o’clock on the photo, an unnamed crater later exposed rocks containing carbonate minerals. The minerals were identified by observations with the mineral-mapping Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on NASA’s Mars Reconnaissance Orbiter.

Carbon dioxide makes up nearly all of today’s Martian air and likely was most of a thicker early atmosphere, too. In today’s thin, cold atmosphere, liquid water quickly freezes or boils away.

Carbonates found in rocks elsewhere on Mars, from orbit and by NASA’s Spirit rover, are rich in magnesium. Those could form from reactions of volcanic deposits with moisture, said James Wray of Cornell University in Ithaca, N.Y. “The broader compositional range we’re seeing that includes iron-rich and calcium-rich carbonates couldn’t form as easily from just a little bit of water reacting with igneous rocks. Calcium carbonate is what you typically find on Earth’s ocean and lake floors.”

He said the carbonates at Huygens and Leighton “fit what would be expected from atmospheric carbon dioxide interacting with ancient bodies of water on Mars.” Key additional evidence would be to find similar deposits in other Martian regions. A hunting guide for that search is the CRISM low-resolution mapping, which has covered about three-fourths of the planet and revealed clay-mineral deposits at thousands of locations.

“A dramatic change in atmospheric density remains one of the most intriguing possibilities about early Mars,” added Mars Reconnaissance Orbiter Project Scientist Richard Zurek, of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Increasing evidence for liquid water on the surface of ancient Mars for extended periods continues to suggest that the atmosphere used to be much thicker.”

Credit: NASA/JPL-Caltech/Univ. of Arizona

The HiRISE image above covers an area about 460 meters (1,500 feet) across in which carbonate minerals have been identified. It combines information collected separately in red, blue-green, and near-infrared wavelengths. It’s from HiRISE observation ESP_012897_168, made on April 27, 2009, and centered at 11.6 degrees south latitude, 51.9 degrees east longitude.

“We’re looking at a pretty lucky location in terms of exposing something that was deep beneath the surface,” Wray said. He reported the latest carbonate findings on Tuesday at the Lunar and Planetary Science Conference near Houston.

Observations in CRISM’s high-resolution mode show spectral characteristics of calcium or iron carbonate at this site. Detections of clay minerals in lower-resolution mapping mode by CRISM had prompted closer examination with the spectrometer, and the carbonates are found near the clay minerals. Both types of minerals typically form in wet environments.

The occurrence of this type of carbonate in association with the largest impact features suggests that it was buried by a few kilometers (or miles) of younger rocks, possibly including volcanic flows and fragmented material ejected from other, nearby impacts.

The new findings reinforce a report by other researchers five months ago identifying the same types of carbonate and clay minerals from CRISM observation of a site about 1,000 kilometers (600 miles) away. At that site, a meteor impact has exposed rocks from deep underground, inside Leighton crater. In their report of that discovery, Joseph Michalski of the Planetary Science Institute in Tucson, Ariz., and Paul Niles of NASA Johnson Space Center in Houston, proposed that the carbonates at Leighton “might be only a small part of a much more extensive ancient sedimentary record that has been buried by volcanic resurfacing and impact ejecta.”

NASA will launch the Mars Atmosphere and Volatile Evolution Mission (MAVEN) in 2013 to investigate processes that could have stripped the gas from the top of the atmosphere into interplanetary space. Meanwhile, CRISM and other instruments now in orbit continue to look for evidence that some of the carbon dioxide in that ancient atmosphere was removed, in the presence of liquid water, by formation of carbonate minerals now buried far beneath the present surface.

Source: NASA news release. See also NASA’s Mars Reconnaissance Orbiter page.