Roller Coaster Ride to Mars

February 6, 2007

SETI Institute Scientists, Nathalie Cabrol and Edmond Grin

June 5, 2003
By Diane Richards
Marketing and Communications Officer

"It has been a roller coaster ride, let me tell you!" is how SETI Institute/NASA Ames scientist, Dr. Nathalie Cabrol describes the nerve-wracking process of selecting a landing site for the NASA's Mars Expedition Rover (MER) mission. At a recent interview in the SETI Institute offices, Dr. Cabrol and Edmond Grin, her scientific partner (and husband), relived the ups and downs of their quest, to secure a visit to an ancient dry lake bed at the end of the Ma'adim Vallis, a huge martian drainage channel.

The combined backgrounds of Cabrol and Grin, in planetary geology and hydraulic engineering, give them a special affinity for the site. Each can visualize the ancient and dynamic processes that most likely formed the martian drainage system with its channels cut by flowing water, and the lake into which the water emptied. Cabrol and Grin were some of the earliest planetary scientists to recognize the tell-tale features of lakes on the Red Planet.

Not Easy Being First

It is not always easy to be first. For nine years, from 1985 to 1994, the duo conducted their planetary geology research at the University of Paris-Sorbonne and Observatory of Paris-Meudon, France. Grin assembled a large "Gusev mosaic" of Viking images that stretched across the wall of their office. The martian landscape caught the eyes of NASA scientist Chris McKay, whose 1994 visit to Meudon coincided with the closure of the lab where Cabrol and Grin worked. Cabrol describes the visit as "a defining moment" as it determined their future. "We left Meudon and followed Chris," she continues. "Edmond packed up the mosaic in his suitcase and we flew to Ames where the mosaic stayed in our cubicle when we arrived and is now archived in our office at the Space Science Division."

With the conviction that Gusev and similar sites were rich with astrobiology potential and thus logical places to visit (ancient lakes are excellent environments for life), Cabrol and Grin pressed on at NASA Ames Research Center, in Mountain View, California. "We had a landing site with no mission," Cabrol explains. What followed was a suite of Mars and Mars-analogue studies supported by several papers on Mars crater lakes. "At the time [between 1994 and 1997], paleolakes were not considered. We had to fight for the notion of crater lakes." The tide began to turn as the evidence mounted with increases in data resolution, and the community of planetary scientists came to accept the idea of impact crater lakes. Meanwhile, the mandate for Mars exploration had become: "Follow the water!" The timing was right.

Thus the MER mission would look for evidence of the past activity of water on Mars, and with the landing site selection process, Cabrol and Grin boarded the "real roller coaster." In January 2001, the first MER landing site workshop, held at NASA Ames, considered a list of 185 potential sites. The preliminary MER landing ellipses, (the landing probability area) were larger than Gusev could accommodate. Knowing this constraint she considered skipping the first workshop altogether.

Process Like Voting

Realizing that the process "is like voting," and that "if you do not vote, you cannot complain if you do not like the result," she submitted her abstract at the very last minute. On day one, Cabrol presented several sites, including Gusev and Gale Craters which both made the first cut. Fortunately, the calibrations determining the size of the ellipse had been refined, and Gusev was now accessible.

The "ride" continued. Cabrol recalls another defining moment during the second workshop in October 2001 in Pasadena. This workshop examined safety issues and heard presentations on the sites' scientific interest. Cabrol pleaded the case of the geologically rich Gusev site. After a first round of votes ten minutes prior to the workshop's end, Gusev's chances looked "uncertain." But then safety issues eliminated two very popular Valles Marineris sites. More presentations and discussions preceded a second round of voting. Gusev made it once again. Says Cabrol, "In five minutes we went from deep concern to our candidate's selection as one of four primary sites. I began to believe something big was going to happen. It was a very deep experience."

Research Becomes Community Effort

Two more workshops in March 2002 and January 2003 would scrutinize the remaining candidates in detail and take the pair up and down their own emotional peaks and valleys before the April 10th announcement of the two final sites: Meridiani and Gusev. Throughout that year and a half Cabrol happily noted that Gusev research had ceased to be "personal." The research was a community effort involving many scientists and engineers. The community scrutinized all of the sites using new data. When the science selection came through, it was unanimous.

Nathalie and Edmond have long advocated crater lakes in general and Gusev in particular as sites of extraordinary scientific interest, notes Christopher Chyba, holder of the SETI Institutes Carl Sagan Chair for the Study of Life in the Universe. Not only are lakes good sites for potential life when theyre wet, after they dry up they are good sites to look for fossil life, because of the sedimentary record they preserve. Nathalie and Edmond fought this battle for so long, sometimes on a personal financial shoestring without much support. Its great that now theyve won the fight, and are in the middle of everything.

If all goes well, soon after landing, MERlike a human infant gazing upon its own toeswill focus its camera upon the rovers front wheels then transmit this first image back to Earth. The view from Mars will be immeasurably more exciting as MER transmits its first panorama of the dry and ancient Gusev lakebed.

Gusev Studies Labor of Love

For Cabrol and Grin, the Gusev studies have been a labor of love that began in 1990, and now, "one revolution of Jupiter later," says Cabrol, "we had the consensus of the science team. That was a very rewarding moment." The SETI Institute, which has partnered with NASA since 1998 on Cabrol and Grin's Mars projects, recently lauded Cabrol and Grin for their work, which represents both the quality and the spirit of wonder that characterizes the interdisciplinary science conducted by the Institute.

"We are not there yet," she reminds us. There are several critical moments between the countdown on June 8, and the moment early in the coming new year when MER opens its 'eyes' and transmits the first image to the expectant team at JPL. Nathalie is equally excited and anxious for the second launch on June 25th, which will take MER B to the second site (the "Hematite") in Meridiani Planum.

For now, however, Cabrol and Grin are smiling. Asked whether she has an idea of what the panorama will look like, Cabrol answers, "Of course." Asked to describe it she smiles coyly and looks at Grin. "Edmond and I will each make a drawing of what we think the site will look like and compare them after the landing." After years of meticulous analysis of the site, each has built a vivid mental image of the placebut for now they have made a pact not to discuss their respective ideas. Comparing their drawings side by side and with the MER images is a private ritual the two scientists look forward to as a celebration of a successful journey they've made together: an exhilarating ride towards Mars.

The Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Exploration Rover project for the NASA Office of Space Science, Washington, D.C.