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Rover findings prompt new search strategy for organics
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: December 9, 2013


Exploring an ancient lakebed on Mars -- a now-vanished, fresh-water lake that increasingly confirms the past habitability of the red planet -- NASA's Curiosity rover is looking for areas where erosion may have uncovered pristine layers in which organic compounds -- and possibly remnant traces of life -- might still be found, scientists said Monday.


This mosaic of images from the Mast Camera (Mastcam) instrument on NASA's Curiosity Mars rover shows a series of sedimentary deposits in the Glenelg area of Gale Crater, from a perspective in Yellowknife Bay looking toward west-northwest. Curiosity's science team has estimated that the "Cumberland" rock that the rover drilled for a sample of the Sheepbed mudstone deposit (at lower left in this scene) has been exposed at the surface for only about 80 million years. See a larger image. Credit: NASA/JPL-Caltech/MSSS
 
"Really what we're doing is turning the corner from a mission that is dedicated to the search for habitable environments to a mission that is now dedicated to the search for that subset of habitable environments which also preserves organic carbon," Principal Investigator John Grotzinger told reporters Monday. "That's the step we need to take as we explore for evidence of life on Mars."

In papers published Monday in the journal Science, the Curiosity team unveiled critical new findings, including measurements of the radiation environment at Mars, which does not have an active magnetic field to shield the surface from its harmful effects.

As it turns out, cosmic rays from deep space can penetrate the upper few feet of martian rocks and soil, breaking apart organic compounds and effectively erasing evidence of past life or the materials necessary for life as it is known on Earth.

To find that evidence, scientists are looking for places along Curiosity's planned route where wind erosion over many millions of years has uncovered underlying beds in the relatively recent past, before energetic cosmic rays have had time to destroy whatever organic compounds might be present.

"Our measurements show that the organics could be preserved at a depth of one meter, even life could possibly, if it existed, survive at a depth of roughly one meter on Mars," said Robert Wimmer-Schweingruber, a co-investigator with the Radiation Assessment Detector on Curiosity.

"It also shows us that as radiation penetrates into the soil ... it reaches the natural background at a depth of roughly three meters. In the top surface layers of four to five centimeters, which (Curiosity) can drill into, it would, with this radiation, reduce the preserved organics by a factor of roughly 1,000 over about 650 million years. So if you want to find organics, you need to find places where it hasn't been exposed for such a long time."

Scientists were able to date a lakebed rock Curiosity drilled into earlier by measuring how an isotope of potassium decayed into argon. The rock in question was formed 3.86 billion to 4.56 billion years ago. It was once buried under many feet of rock and soil, but the martian winds slowly eroded the upper strata, bringing it into reach of Curiosity's drill.

Ken Farley, a Curiosity researcher with the California Institute of Technology, said an analysis of the drill sample showed the erosion happened relatively recently, over the past 60 million to 100 million years, and that about three feet of strata is removed every million years or so.

The relatively recent uncovering of the lakebed clays "suggests that there will be some organic degradation, but perhaps not extensive organic degradation," Farley said. "But more importantly, we now have a model of where to look for the least cosmic ray irradiated rock we can get to. We simply drive to the downwind scarp and drill at the base of that scarp."

By drilling within three feet or so of a scarp, or ridge line, where the martian wind has uncovered lower layers, "we might get surface exposure ages, cosmic ray dosages, of only about a million years."

If so, Curiosity would have a much better chance of detecting complex organic compounds.

"Our hypothesis is that we can decrease the surface exposure age by drilling right up at those edges," Farley said. "And then we can test that hypothesis by obtaining the surface age date. That's our goal as we go forward here and we think the big step for the mission that takes us closer to the search for life on Mars is being able to reduce this risk of radiation, which is a very Mars-unique process."

Curiosity landed in Gale Crater in August 2012. Since then, it has been slowly making its way toward a towering mound of layered rock in the heart of the crater known as Mount Sharp, stopping along the way to investigate intriguing formations.

One such site is known as Yellowknife Bay, where Curiosity's power drill collected samples confirming a once-habitable environment. Scientists do not yet know the full extent of the lake they now believe existed there, but it likely stretched at least 30 miles around the base of Mount Sharp.

"Imagine something, an environment you might have had back on Earth about .... 10,000 years ago," Grotzinger said. "Cool, cold, maybe even ice available at the time. ... The size of these lakes would have been like the small finger lakes of upstate New York, something like that.

"The important thing we learned about the chemistry, with the clay minerals forming there, we have a moderate to neutral pH. Also we know from the absence of salt in the rock ... that lake didn't have a lot of dissolved salt in it. And finally, we have the kinds of chemicals and minerals that would have allowed simple micro-organisms to live in that environment."

In the absence of oxygen, such micro-organisms likely would have had to get by with a process known as chemolithotrophy, or "eating rock" as a summary in Science put it.

But finding actual fossils, or any remnants of ancient microbial life, assuming any are there to be found, will remain a major challenge.

"The key thing here is that ... if you go back into rocks that are billions of years old and ask what remnants of life there are, it is rare, rare, rare to find an actual microfossil," Grotzinger said. "It is a little bit less rare to find a large organic molecule. We call those chemofossils.

"And so, the trick is to make sure you have enough of the good minerals and as little as possible of the bad chemical compounds that will (alter) them. That's the game we're now weighing in on, in addition to quantifying radiation exposure."

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VIDEO: THE MARS SCIENCE LAB FULL LAUNCH EXPERIENCE PLAY | HI-DEF
VIDEO: ATLAS 5 ROCKET LAUNCHES MARS SCIENCE LAB PLAY | HI-DEF
VIDEO: ONBOARD CAMERA VIEW OF NOSE CONE JETTISON PLAY | HI-DEF
VIDEO: ONBOARD CAMERA VIEW OF THE STAGING EVENT PLAY | HI-DEF
VIDEO: ONBOARD VIEW OF ROCKET RELEASING MSL PLAY
VIDEO: LAUNCH DECLARED A SUCCESS PLAY

VIDEO: LAUNCH REPLAYS: OUR VIEW OF LIFTOFF PLAY | HI-DEF
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VIDEO: LAUNCH REPLAYS: SOUTH OF THE PAD PLAY | HI-DEF
VIDEO: LAUNCH REPLAYS: THE BEACH TRACKER PLAY | HI-DEF
VIDEO: LAUNCH REPLAYS: SHUTTLE PAD CAMERA PLAY | HI-DEF
VIDEO: LAUNCH REPLAYS: SHUTTLE WATER TOWER PLAY | HI-DEF
VIDEO: LAUNCH REPLAYS: TRACKER WEST OF THE PAD PLAY | HI-DEF
VIDEO: LAUNCH REPLAYS: CLOSE-UP ON UMBILICALS PLAY | HI-DEF
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VIDEO: LAUNCH REPLAYS: THE PRESS SITE PLAY | HI-DEF

VIDEO: PRE-LAUNCH INTERVIEW WITH PROJECT MANAGER PLAY | HI-DEF
VIDEO: NARRATED PREVIEW OF ATLAS 5 ASCENT PROFILE PLAY | HI-DEF
VIDEO: ROCKET'S LAUNCH CAMPAIGN HIGHLIGHTS PLAY | HI-DEF
VIDEO: MSL'S LAUNCH CAMPAIGN HIGHLIGHTS PLAY | HI-DEF
VIDEO: SPACECRAFT CLEANROOM TOUR PLAY | HI-DEF

VIDEO: ATLAS ROCKET ROLLS OUT TO LAUNCH PAD PLAY | HI-DEF
VIDEO: TIME-LAPSE VIEWS OF ROCKET ROLLOUT PLAY | HI-DEF

VIDEO: THE PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: CURIOSITY ROVER SCIENCE BRIEFING PLAY
VIDEO: LOOKING FOR LIFE IN THE UNIVERSE PLAY
VIDEO: WHAT WE KNOW ABOUT THE RED PLANET PLAY
VIDEO: ROBOTICS AND HUMANS TO MARS TOGETHER PLAY

VIDEO: PREVIEW OF ENTRY, DESCENT AND LANDING PLAY | HI-DEF
VIDEO: PREVIEW OF CURIOSITY ROVER EXPLORING MARS PLAY | HI-DEF
VIDEO: A FLYOVER OF THE GALE CRATER LANDING SITE PLAY | HI-DEF

VIDEO: NUCLEAR GENERATOR HOISTED TO ROVER PLAY | HI-DEF
VIDEO: MARS SCIENCE LAB MOUNTED ATOP ATLAS 5 PLAY | HI-DEF
VIDEO: MOVING MSL TO ATLAS ROCKET HANGAR PLAY | HI-DEF
VIDEO: SPACECRAFT PLACED ABOARD TRANSPORTER PLAY | HI-DEF

VIDEO: APPLYING MISSION LOGOS ON THE FAIRING PLAY | HI-DEF
VIDEO: MSL ENCAPSULATED IN ROCKET'S NOSE CONE PLAY | HI-DEF
VIDEO: FINAL LOOK AT SPACECRAFT BEFORE SHROUDING PLAY | HI-DEF

VIDEO: HEAT SHIELD INSTALLED ONTO SPACECRAFT PLAY | HI-DEF
VIDEO: BEAUTY SHOTS OF SPACECRAFT PACKED UP PLAY | HI-DEF
VIDEO: ATTACHING THE RING-LIKE CRUISE STAGE PLAY | HI-DEF
VIDEO: PARACHUTE-EQUIPPED BACKSHELL INSTALLED PLAY | HI-DEF
VIDEO: SKYCRANE AND CURIOSITY MATED TOGETHER PLAY | HI-DEF

VIDEO: TWO-HALVES OF ROCKET NOSE CONE ARRIVES PLAY | HI-DEF
VIDEO: CENTAUR UPPER STAGE HOISTED ATOP ATLAS PLAY | HI-DEF
VIDEO: FINAL SOLID ROCKET BOOSTER ATTACHED PLAY | HI-DEF
VIDEO: FIRST OF FOUR SOLID BOOSTERS MOUNTED PLAY | HI-DEF
VIDEO: FIRST STAGE ERECTED ON MOBILE LAUNCHER PLAY | HI-DEF
VIDEO: STAGES DRIVEN FROM HARBOR TO THE ASOC PLAY | HI-DEF
VIDEO: ROCKET ARRIVES ABOARD SEA-GOING VESSEL PLAY | HI-DEF

VIDEO: STOWING ROVER'S INSTRUMENTED ROBOT ARM PLAY | HI-DEF
VIDEO: DEPLOYING CURIOSITY'S SIX WHEELS ON EARTH PLAY | HI-DEF
VIDEO: MMRTG PUT BACK INTO STORAGE AT SPACEPORT PLAY | HI-DEF
VIDEO: NUCLEAR GENERATOR FIT-CHECK ON THE ROVER PLAY | HI-DEF
VIDEO: ROVER'S NUCLEAR POWER SOURCE ARRIVES PLAY | HI-DEF
VIDEO: SPIN-TESTING THE RING-LIKE CRUISE STAGE PLAY | HI-DEF

VIDEO: UNCOVERING CURIOSITY ROVER IN CLEANROOM PLAY | HI-DEF
VIDEO: UNVEILING THE ROCKET-POWERED SKYCRANE PLAY | HI-DEF
VIDEO: UNBOXING THE ROVER FROM SHIPPING CRATE PLAY | HI-DEF
VIDEO: ROVER HAULED FROM RUNWAY TO PHSF FACILITY PLAY | HI-DEF
VIDEO: MARS ROVER ARRIVES AT KENNEDY SPACE CENTER PLAY | HI-DEF

VIDEO: DESCENT WEIGHTS INSTALLED ON BACKSHELL PLAY | HI-DEF
VIDEO: SOLAR ARRAY PANELS ATTACHED TO CRUISE RING PLAY | HI-DEF
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