Editorial: “There may already be aliens on Mars“
TO FIND life on Mars, we need to stop being so overprotective of our smaller sibling. So argue two Mars scientists behind a controversial new push to relax planetary protection rules – a set of sterilisation procedures that Mars-bound spacecraft must undergo to avoid contaminating the planet with terrestrial microbes.
The existing rules have made missions that would probe for Martian life costly and inefficient, the pair argues in an editorial published last week in Nature Geoscience (). Also, no sterilisation system is perfect, so chances are we have already contaminated Mars with trace amounts of earthly microbes carried by our rovers and landers.
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What’s more, we may soon have a good way to tell the difference between native Martians and Earth-born life. A compact DNA sequencer is being developed that would be ready in time to fly with NASA’s next Mars rover, slated for launch in 2020.
Today’s planetary protection rules got their start in a 1967 UN treaty. Specific procedures are set and updated by a Paris-based group called the Committee on Space Research (COSPAR). The requirements vary depending on the mission, but the most stringent measures can include heating spacecraft parts to kill most microbes aboard, and keeping sterilised parts in protective wrappings until after landing on a cosmic body.
The 1976 Viking missions were the first to look specifically for life on Mars, and the two spacecraft went through careful sterilisation, including being baked whole at 111.7 °C. Viking’s cost was $1 billion, with over $100 million of that spent on protection measures.
The requirements have been relaxed somewhat since Viking, but they are still redundant and wasteful, says astrobiologist Dirk Schulze-Makuch of Washington State University in Pullman, who co-authored the editorial. “Right now it has this bad effect,” he says. “It hampers missions – especially the interesting missions.”
“Right now, protection has this bad effect. It hampers missions – especially the interesting missions”
Schulze-Makuch and planetary scientist Alberto Fairen of Cornell University in Ithaca, New York, think it is even possible that organisms from Earth got to Mars with no help from us. Meteorites tossed between the two planets early in the solar system’s history may have brought microbes with them, which could have survived the journey.
“In general I’m sympathetic to the editorial’s argument,” says Ryan Anderson of Los Alamos National Laboratory in New Mexico, who works on NASA’s Curiosity rover. It is a bit of a paradox, he says, that the rules make the most habitable parts of Mars the toughest places to send new spacecraft to.
Proponents of sterilisation have been quick to strike back, arguing that the protection measures keep planetary expeditions from wasting time and resources on false detections of signs of life. Such measures also prevent irrevocable alterations to potential alien ecosystems, either on Mars or on other promising spots for finding life (see “Keep Europa tidy, please“).
“One of the purposes of planetary protection is to help keep us from suffering the consequences of our own ignorance,” says NASA planetary protection officer Catharine Conley. She adds that including such measures adds little to the overall budget of a modern big-ticket mission such as the Curiosity rover, which cost about $2.5 billion. The procedures also force better design and more rigorous testing.
“Many of the requirements pre-landing also overlapped with those necessary for Curiosity to make sensitive and robust detections of Mars’s chemistry, particularly any organic materials,” says Ashwin Vasavada, Curiosity’s deputy principal investigator.
But if we do contaminate Mars, at least we have a backup plan. , based at the Massachusetts Institute of Technology, aims to send a DNA sequencer to the planet. Such a device would be able to distinguish any uniquely alien components of genetic code from those of, say, a hitch-hiking microbe from Earth.
The sequencer could also tease out whether Martian life, if discovered, was a distant cousin of Earth life that arrived on a meteor millions of years ago and adapted, says Chris Carr of MIT. “We’re not quite there yet, but with the technologies that exist today, we could do it.”
One thing is for sure: planetary protection will be a moot point when humans arrive on Mars, with all their attendant bacteria.
“There are opportunities to study life on Mars now, and when humans do get there, there are certain questions we will no longer be able to answer,” says Conley. “It’s going to be a race against time.”
Keep Europa tidy, please
Even if we stop coddling Mars, other parts of the solar system will still need to be handled with kid gloves.
Many icy moons, for instance, may also host extraterrestrial life but they are much less likely to have swapped microbes with Earth (see main story). Chief among these is Jupiter’s moon Europa, which is a planetary-protection disaster waiting to happen, says of the SETI Institute in Mountain View, California.
The large moon probably hosts a global ocean beneath a thick icy crust. Evidence for cracks in the ice suggests that liquid may be moving between the ocean and the surface. That’s great news for alien hunters, who hope that by receiving oxygen and nutrients from Europa’s surface, the ocean could host diverse life.
“But if you contaminate one part of Europa and it gets down to the ocean, you’ve contaminated the entire ocean,” says Phillips.
When the Galileo spacecraft ended its mission in 2003, it plunged into Jupiter’s atmosphere to avoid colliding with and polluting Europa. So how can we intentionally send something that will reveal the moon’s secrets without damaging any potential ecosystems?
Proposed Europa orbiters could save enough fuel to make a nosedive into Jupiter when the mission ends, or they could make sure they orbited Europa for years, so that radiation from Jupiter fried any remaining on-board microbes.
“It’s a fine line. We want to protect and preserve Europa, but we still want to be able to go there,” says Phillips. “We don’t want to put a giant fence around the whole Jupiter system and say no, you can’t go anywhere near it.”
Similar concerns apply to Saturn’s moon Enceladus and Neptune’s moon Triton, which also probably host oceans beneath icy crusts.
This article appeared in print under the headline “Go ahead rovers, contaminate Mars”
