From the "JPL Universe"
October 4, 1996
Excitement about the exploration of Mars has never been higher, both inside and outside of JPL. The speculation and arguments posed for centuries by scientists and scholars about the possibility of life on the Red Planet have been revived with the announcement in August of possible evidence found in an ancient meteorite in Antarctica.
At JPL the implications could be huge. "There's no question in my mind that Mar's exploration will play an even more important role in JPL's future than we had imagined even as little as a year ago," said Dr. Daniel McCleese, manager of the Earth and Space Sciences Division 32. "We can say that with confidence." It is not, however, as if the Mars Surveyor program has proceeded without direction, needing the boost provided by the Mars meteorite discovery, McCleese was careful to point out. He said that the path currently traveled by the program has been the right one all along. "I think we've had enough time since the announcement of the Mars meteorite studies to evaluate the Mars program JPL has been pursuing," McCleese said. "A broad consensus is that if we were to invent a program today, without any of the past studies we've done on how Mars should be explored, you would probably come up with a program that looks very much like Mars Surveyor."
This spring, McCleese led a NASA team studying the feasibility of returning scientifically significant samples from Mars as early as the 2005 mission, within the budget that's already been allocated by Congress for the Mars Surveyor program. McCleese's team reported to the agency that a sample return mission launched in 2005 could be accomplished within Mars Surveyor's present budget of approximately $ 100 million per year plus launch costs. "We also said, however, that the program would become very lean," McCleese said. "The amount of money available requires reducing the number of launches per opportunity from the baseline of two vehicle launches to one. Also, we judged that extra money would be needed for technology development for a rover that we wanted to send as a precursor to the sample return. "This was considered by NASA to be fairly good news; that it looked as if we could come pretty close to making it within the budget." With the announcement of possible evidence of past life in the ALH84001 meteorite, McCleese's team, called the Mars Expeditions Strategy Group, regrouped and focused its efforts on a program to find evidence of life, if it exists, on the surface of Mars.
The group worked closely with JPL's Mars Program Office and the Advanced Projects Design Team ("Team X"), which provided analyses of the costs of quicker sample return missions than originally proposed. Together, they developed strategies to implement three different program options -- called "paced," "accelerated," and "aggressive" -- as suggested by NASA Administrator D Daniel Goldin.
"Goldin asked for these options because of the interest by the White House and the nationwide enthusiasm for exploration of Mars, possibly at a greater rate than we're able to do under the Mars Surveyor program," McCleese noted. The "paced" approach proposes a launch in 2005, with a sample returned to Earth by 2008. The "accelerated" option proposes a 2003 launch, with a sample return by 2006, while the "aggressive" option would launch a Mars surface "field geologist" rover to Mars in 2001 as well as return a sample by 2006.
Each option includes visiting three different sites, or environments, on Mars and returning a sample from each site. The group described the scientific objectives and approach for the search for life on Mars, as well as the need for evolving technologies, costs and the rate at which each option would be accomplished.
The recommendations were developed at a late-August meeting of 30 scientists, technologists and engineers from NASA and several universities. That group met again Sept.19-20 to confirm a report it had begun to create at the previous meeting. "We also evaluated and modified the implementation strategies that JPL's Mars Program Office had created over the prior several weeks " McCleese said. "Now we have an outline of elements identified for each of the three sample return options Goldin suggested." The group's findings were presented Sept. 30 to NASA's Solar System Exploration Subcommittee, which advises the agency on solar system exploration planning.
McCleese said that sample return missions to Mars, whether or not they will be stepped up from the original 2005 target for the first launch, would not fundamentally change the overall goals of the Mars Surveyor program, but would be an extension of those goals with a stronger emphasis on life than on the program's other goals of studying climate and resources.
"We are charged by Dan Goldin with designing a program to understand the origin and evolution of life on the planet -- if it ever existed within the context of the evolution of Mars itself," McCleese said. "We are interested in studying the planet through robotic means. And our robots are intended to explore the planet's geochemistry, geology, and climate. In so doing, we will determine which samples are most scientifically productive to return to the Earth."
McCleese outlined the plan for the study of the global character of the planet -- its geochemistry and evolutionary processes at the surface and in the interior. Noting that one of the fundamental requirements for life is water, he said the search will be conducted by looking at three environments:
McCleese said the debate on ALH4001 will continue for years, "so we do not consider that to be evidence yet. We consider it to be hopeful and suggestive -- that the environment on Mars might have been conducive to the development of life."
If further analysis of the Mars meteorite determines that life was not present, that would not halt studies of the planet. "We are equally interested in in understanding why life did not form if it didn't," McCleese said. "Is life unique to the Earth? We propose to study each environment so that we can understand this possible dichotomy with Earth: is Mars a planet that has undergone the same kind of evolutionary processes as Earth has, or is it completely different?" Just as critical to getting a spacecraft to Mars, gathering samples of its surface, and returning it to Earth will be sample analysis done in laboratories on Earth.
"The experiments we need to do with samples are not practical to do on the surface of Mars," McCleese noted, adding that analysis of samples "figures very prominently in our exobiology goals as they refer directly to possibly prebiotic components, or some day, perhaps, fossils." In that regard, McCleese expressed concern that a too highly aggressive approach might result in a program "that is not scientifically motivated, but is motivated simply by the desire to get things into space and on the planet."
"We could very well disappoint ourselves in that we might not be able to locate the sites where life-related samples may come from, because we might not have adequate sensors onboard the rovers, adequate mobility of the rovers or the skill needed in acquiring and handling the samples to get back relevant samples.
"In a laboratory on Earth, you're wholly dependent on the quality of the work done on Mars, particularly on the quality of the returned samples. A 'grab' sample -- one selected without care -- is exceedingly risky if we are searching for the markers of life."
Whichever options are followed, confirmation that life never evolved on Mars, even in its simplest forms, would not be met with disappointment in some circles or a lull in Mars exploration as it was with the Viking missions of the mid-'70s.
"Clearly, finding fossil evidence on Mars would motivate an aggressive program of exploration," McCleese said. "But it's my view that the discovery that may one day motivate aggressive exploration of Mars has already happened." "Broadly speaking," McCleese added, "the Mars meteorite findings have already heightened public interest in exploring deeper questions, like the origins of life in the universe," he said. "This goal may rise to the top of the list of planetary exploration objectives."