An artist's conception shows a SpaceX Dragon capsule firing its retros to land on Mars. Scientists hope to use an advanced Dragon and a Falcon Heavy to deliver a life-detection experiment to Mars.
NASA officials emphasize that the Curiosity rover is not designed to look for signs of life on Mars, but other researchers say it could come across those signs in spite of itself — and still others are planning experiments to take on the "life on Mars" question directly for the first time in decades.
Every time the question comes up, it stirs a controversy: It was that way in 1976, when some of the researchers working on the Mars Viking mission contended that they saw evidence of biological activity on the Red Planet. It was that way in 1996, when researchers at Johnson Space Center said they spotted nanofossils inside a meteorite from Mars. And it was that way in 2004, when other researchers suggested that whiffs of methane detected on Mars hinted at the presence of life.
Perhaps because of those controversies, NASA tends to downplay the question during the current Curiosity campaign. "Whether life has existed on Mars is an open question that this mission, by itself, is not designed to answer," the mission's press kit declares. But Gil Levin, who still argues that Viking discovered life on Mars, believes Curiosity could confirm the discovery.
He says one of Curiosity's chemistry analyzers, known as Sample Analysis at Mars, or SAM, could detect organic compounds that would fill in the pieces that were missing during the Viking mission. And he's hoping that Curiosity's high-resolution color cameras will pick up the spectral signature of lichen-type growth on Martian rocks. Such organism might well have hitchhiked to Mars on meteorites that were blown into space from Earth.
"Preserved, frozen, they could survive the entry to Mars and grow under Martian conditions," he told me a few months ago.
Follow the methane
Robert Zubrin, a rocket scientist who's the president of the Mars Society, has a different perspective but arrives at the same bottom line when it comes to Curiosity. "It has the ability, in my view, to detect life on Mars," he told a Mars Society gathering on Saturday night.
The SAM analyzer not only has the capability to detect methane in the Martian atmosphere, but can also break down the distribution of different carbon isotopes to determine whether the gas was created through biological or purely geochemical processes, Zubrin said. "It could catch the scent of life on Mars," he said.
Even John Grunsfeld, NASA's associate administrator for science, acknowledged today that the analysis of Martian methane was one of the promising avenues of research available to Curiosity. Because methane tends to be broken down relatively quickly, the supply in the Martian atmosphere has to be replenished regularly. Emanations from volcanoes or gas hydrates could do it, but so far there's little evidence of that type of activity on Mars.
On Earth, much of the atmosphere's methane comes from biological sources, such as the digestive tracts of cows. Grunsfeld joked that if there were cows on Mars, the resolution of the camera on NASA's Mars Reconnaissance Orbiter is so good that "we would have seen them." But microbes? If Curiosity even hints that biology may be responsible for Martian methane, that could well become the prime focus of future Red Planet missions.
Drilling for life
Some NASA scientists and engineers are already thinking about those future missions. For example, Carol Stoker, an astrobiologist at NASA's Ames Research Center, is part of a team that's drawing up a proposal for a life-detection mission known as Icebreaker. During this week's Mars Society conference, Stoker said it was "quite possible that there is modern life on Mars," based on the chemical analyses conducted by NASA's Phoenix Mars Lander in 2008.
She'd like to see Icebreaker return to the north polar region visited by Phoenix, carrying a drill as well as a device known as a Signs of Life Detector, or SOLID for short. SOLID uses a microarray with hundreds of different antibodies to test for the presence of a wide variety of microbes, including the sorts of extremophiles that some experts think could survive beneath the surface on present-day Mars.
"We believe we can answer the question, 'Is there Earthlike life at that site,' with a Discovery-class mission" costing no more than $425 million, Stoker said. She said a proposal could be prepared for NASA's next solicitation for Discovery-class or New Horizons missions, whenever that happens.
To hit that price tag, the experiment would be launched inside a next-generation SpaceX Dragon capsule, atop a next-generation Falcon Heavy rocket. The plans for a "Red Dragon" trip to Mars made a splash last year, but a lot of the technologies to back up the concept have yet to be developed. The Falcon Heavy is still under development, for example, and the proposed landing scenario for the Dragon relies on a system called supersonic retro propulsion.
"That's at a relatively low technology level," Doug McCuistion, director of the Mars Exploration Program at NASA Headquarters, told me today. But some smart people are studying how to make the mission concept work — including Adam Steltzner, the head of the group at NASA's Jet Propulsion Laboratory that developed the unorthodox sky-crane system for putting Curiosity on the ground.
Could it work? And is it plausible to think biochemical tests at a single site could turn up evidence of life on Mars? Or is NASA's deliberate, step-by-step approach the way to go? Feel free to weigh in with your comments below.
More about Mars:
- Mars Curiosity comes in for a landing
- Last-minute guide to the Mars landing
- What will we see from Mars, and when will we see it?
- Why we're obsessed with Mars
- Mars probe provides radiation revelations
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.