Curiosity Will Eye Evidence For Life As Distance to Mountain Shortened

Artist's rendering depicts Curiosity using its arm mounted science turret to investigate Martian rocks. Image Credit: NASA

Science team members for the new Mars rover Curiosity will use the rover’s powerful cameras to specifically look for visible evidence of past life on Mars, like the 3.5 billion year old fossilized microbe “stromatolite” colonies found on Earth.

“There are a number of people on the team interested in this question” of finding evidence for life with Curiosity, said John Grotzinger, Mars Science Laboratory (MSL) project scientist, at the California Institute of Technology, Pasadena, Calif.  “It tends to come up quite a bit” in the science team, Grotzinger said at a NASA briefing on MSL readiness.

Curiosity, set to land Aug. 5 at 10:31 p.m. Pacific Time, is not designed as a life detection mission.

NASA Public Affairs and MSL managers have pressed the non life detection theme throughout the MSL development.

The project, however, has recently acknowledged the importance of serendipitous discovery in scientific breakthroughs and the importance true evidence of Martian life would have for science, religion, NASA’s future and public interest in space.

Curiosity's science team will look for rocks like these 3.5 billion year old stromatolites discovered in Australia. They are formed by colonies of bacteria. Note lens cover for scale. Photo Credit: NSF

Grotzinger said that because the Gale Crater landing target was a water rich environment early in Martian history,  it is possible that multibillion groups of microorganisms, primarily cyanobacteria, solidified there into rocks with distinctive patterns. But that would raise the same question as arises on Earth, whether the striking rock patterns are always indicative of past life, the MSL science manager says.

“If they are at this site we would expect to see those with our cameras and be challenged with the same questions we have about them on Earth, whether they constitute definitive evidence for the presence of past life,” said Grotzinger.

“I think that we would be thrilled enough to actually see something like that to warrant a Martian sample return mission, ” he said.

“As for chemistry we have the capability with the Goddard SAMS Sample Analysis At Mars instrument, to differentiate carbon isotope ratios,  so if there was something alive in the past we expect to see evidence of that. But again it would fall short of definitive evidence for life but also be provocative enough to warrant a sample return mission,” said Grotzinger.

Computer generated overhead view of Gale Crater Mt. Sharp at center and at its base the original lighter and larger landing ellipse and the darker much tighter ellipse closer to the mountain flanks. Image Credit: NASA

A significant improvement in MSL landing targeting just achieved at the Jet Propulsion Laboratory will also benefit mission science return by placing the rover closer to its planned route up Sharp Mountain in the center of Gale Crater.

The original landing ellipse with the target in the center was 12 mi. wide x 16 mi. long, itself much smaller than previous Mars landing zones. But continuing analysis of the new MSL  landing system capabilities has allowed mission planners to shrink the area to approximately 4 mi. wide  x 12 mi. long.

“We’re trimming the distance we’ll have to drive after landing by almost half,” said Pete Theisinger, Mars Science Laboratory project manager at NASA’s Jet Propulsion Laboratory, Pasadena. “That could get us to the mountain months earlier.”

All of this has been done by shrinking the size of the landing ellipse that new testing and analysis indicate is now possible to achieve. The team then moved the new ellipse and its center target point closer to the mountain. (See graphic below) This may cut the time it takes to drive from the target point to reach the side of the mountain by 4 months Theisinger said.



Curiosity's darker line new landing ellipse is just 4 x 12 mi. compared with 12 x 16 mi. larger older ellipse. The new target point is 4 mi. closer to the mountain saving Curiosity 4 months of driving. Image Credit: NASA

“To achieve this we did a lot of computer analysis runs of  Entry Descent and Landing (EDL) with real flight software  using dispersed wind models and really good statistics on the landing hazards,” Theisinger said.

He said the EDL team found that the margins in the landing ellipse were more conservative than they needed to be.

The second thing the team did was address a key parameter in landing error, the attitude determination the spacecraft makes when entering the atmosphere.

Because unlike the Viking 1 & 2, Pathfinder, Spirit, Opportunity and Phoenix aeroshells, Curiosity’s  much larger aeroshell  uses a totally different guided entry design  where the aeroshell ejects ballast to alter its center of gravity and lift vector during the descent . This enables it to generate positive lift and actually fly rather than fall ballistically to the landing site, as did Viking and everything since until MSL.

JPL's three rover designs show how the technology has matured from the 1997 Pathfinder rover at foreground, a Mars Exploration Rover at left and Curiosity mockup at right. Photo Credit: NASA

The MSL spacecraft flies under inertial measurement unit (IMU) control to the landing site, so the errors that exist at the very beginning of that process—navigation error and attitude error– are the two elements that can cause the landing area to either grow or shrink by some margin.

“Our in flight calibration of the attitude determination error [made during trajectory correction maneuvers ] have been extremely positive so we decided to use some of that margin as well,” said Theisinger.

That allowed the team to shrink ellipse—and having shrunk it,  then move it toward Mt. Sharp in a direction that avoided the terrain hazards as much as possible.

“This gets us quicker to the base of Mt. Sharp where the primary science targets are,”  said Grotzinger.

Curiosity is depicted firing its laser at a rock to assess the resulting plasma flash for compositional data. At right its manipulator arm holds powerful science turrent with sampling drill hampered by Teflon contamination generated internally which could affect samples.  Image Credit:   NASA-JPL-CalTech.


One Comment

  1. Thank you very much Craig for the very informative and well-written article. As is the standard for AmericaSpace, the work is exemplary and most entertaining. I am eagerly looking forward to the August landing of Curiosity, and have a bottle of Scotland’s finest set aside for the celebration. It gives one pause to consider that in four million years of human evolution producing one hundred thousand generations of ancestors, we are the fortunate ones to be at the front of that long, stadium-filling line of our relatives (O.K., some being hairier with thicker brow ridges than others) to enjoy this history-making NASA engineering genius. Right on Dr. Neil deGrasse Tyson!!

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