Search for Organics Ramps Up after Mars Rover Hit Paydirt

by

CAPE CANAVERAL, Fla. — With one life-friendly environment found on Mars, scientists using NASA’s Curiosity rover are retooling for Mount Sharp, the primary target of the mission, which is intended to assess if the planet most like Earth in the solar system has or ever had the chemistry and environments for microbial life.

Hitting paydirt on the very first analysis of a sample powder drilled out from inside a rock near the rover’s Gale Crater landing site raises the stakes for similar analysis on Mount Sharp, a 5-kilometer high mound of what appears to be layered sediment rising from the crater’s floor. Though Mount Sharp is why Gale Crater was selected as the landing site, the rover first explored a region known as Yellowknife Bay located in the opposite direction.

“We just didn’t stumble into this area. This was something that took a lot of planning,” said Curiosity lead scientist John Grotzinger of the California Institute of Technology.

“In case something happened with the rover we needed to make sure we had science to do in that landing ellipse. That was a backup, a secondary objective. What was serendipitous was landing in a past aqueous environment and finding sulfates and clays,” he said.

The sample showed the rock contains six elements needed for microbial life — hydrogen, carbon, oxygen, nitrogen, sulfur and phosphorus — plus water that had not been too acidic or too salty.

A pair of computer glitches suspended rover operations in March before scientists could drill out a second sample to verify the results. Curiosity, as well as all other spacecraft on and around Mars, is now in a monthlong radio communications blackout with Earth because of the sun’s position between the planets.

When the planets realign on May 1, scientists plan to take a second stab at looking for organic carbon in the Yellowknife Bay area before driving the rover toward Mount Sharp. The carbon found in the first sample was bound in carbon dioxide, which is not a problem for some rock-eating microorganisms on Earth.

“With the issue of habitability in the bag, we can undertake a systematic search for a brighter carbon signal. The search for organic carbon is an issue for this mission and you want to do this as deliberately as possible. You don’t want to just wander around and try stuff out,” Grotzinger said.

Whether or not indigenous life ever evolved on Mars, at some time the planet should have had organic compounds delivered to its surface by organic-rich comets and asteroids. Finding places where the organics could have been preserved, however, is a much trickier prospect than finding environmental niches and chemistry needed to support life.

“On Earth, finding organics in very, very ancient rocks is a difficult proposition,” said NASA Goddard Space Flight Center’s Paul Mahaffy, lead scientist for the rover’s Sample Analysis at Mars experiment.

The problem is that many of the same processes that create rocks destroy organics.

“It’s just risky business to try to predict where the organic carbon may be. We are motivated to do it for the simple and obvious reason that we know there’s a flux that comes from outer space onto the planet,” Grotzinger said.

Organic carbon may not be found on Mars because the concentrations are too low, or because the carbon broke down over time either by chemical alterations or from solar and cosmic radiation.

“The hope is we find some other examples of habitable environments. There are a bunch of different geological reasons why there could be more or less carbon in one place,” Grotzinger said.

Yellowknife Bay is in a lowlands area and likely was once covered with water. Scientists, however, have no context for dating when that might have occurred, or what happened previously.

Mount Sharp, by comparison, offers scientists a ladder in time, with the record of older events preserved at the bottom of the mound and more recent alterations of the rock rising above.

“Say we find something that looks like another attractive ancient potentially habitable environment and it’s 200 meters above the base of Mount Sharp,” Grotzinger said. “We can go up there and then from there we can go not just upward but also downward again. So if you’re looking for something, you can explore in both directions of time’s arrow.

“Right now, (in Yellowknife Bay) we’re in the good stuff, but unfortunately, we can’t go downhill anymore. We’re there. That’s all Yellowknife Bay is going to give us.”

Curiosity, which touched down Aug. 6, is eight months into a planned two-year mission.