Newest NASA discoveries could boost search for life on Mars
In puffs of gas from rocks more than 3 billion years old dug up by one of NASA’s robotic explorers on Mars, scientists have identified several complex organic molecules— possible building blocks for ancient life.
It’s not aliens. (It’s never aliens.)
But it is “consistent with the past presence of biology,” said Ken Williford, an astrobiologist at NASA’s Jet Propulsion Laboratory. “Anditmakes usmore confident that if biomarkers” — or direct evidence of biologic activity— “are there, we might find them.”
In two studies published Thursday in the journal Science, this new finding from NASA’s Curiosity rover is paired with another discovery: The planet’s methane — another organic molecule usually ( but not always) produced by living beings — varies with the seasons. In the past, scientists have seen plumes and patches of this intriguing substance, but this is the first time they’ve been able to discern a pattern in its presence. The result could pave theway for futuremissions to pin down the methane’s source.
“The closer we look, the more we see that Mars is a complex, dynamic planet that — particularly early in its history — was more conducive to life than we might have previously imagined,” said Williford, whowasnot involved in either study.
A reminder: Organic molecules aren’t necessarily produced by organisms; they’re just chemical compounds that contain carbon. But they’re of interest to astrobiologists because they are the essential ingredients in all the chemistry that drives life on Earth.
Mars’ Gale Crater, where Curiosity has been trolling around for the past six years, is a particularly interesting place to look for thosemolecules. About 3.5 billion years ago, research suggests, this pockmark on the Martian surface was brimming with water.
But the water vanished when most of the Martian atmosphere was stripped away by brutal solar winds. And, given the intensity of the radiation bombarding the planet’s surface, it wasn’t clear whether any relics fromthat warm, wet period could still be preserved inmudstones on the lake’s dried-up floor.
Using Curiosity’s Sample Analysis at Mars instrument — which heats soil and rock samples to examine their contents— astrobiologist Jennifer Eigenbrode and her colleagues were able to identify an array of interesting organic molecules: Ring structures known as aromatics, sulfur compounds and long carbon chains. Even more compelling was the fact that these compounds seemed to have broken off even bigger, more complex “macromolecules” — substances found on Earth in coal, black shale and other ancient organic remains.
There are some non-biological explanations for the detection — this combination of compounds has also been found in meteorites. But that explanation, too, suggests a provocative possibility; even if the organic molecules didn’t come from life, they are exactly what life likes to eat. Perhaps the meteorite- delivered molecules provided fuel for ancient alien organisms.
Regardless, the detection is a technical achievement, said Williford, because it demonstrates that organic molecules can persist near Mars’ surface for billions of years.
If scientists keep drilling deeper and more widely, as they plan to do with the European and Russian space agencies’ ExoMars rover and NASA’s Mars 2020 mission, who knows what they might find?
( Williford is deputy project scientist for Mars 2020.)