A new device could significantly speed up the search for life on Mars.
Using a green laser to scan surfaces for evidence of past or present life, the Stanoff Biofinder can, in less than a second, detect organisms as small as microbes from several feet away. The instrument, named for its fast, hands-off approach to finding life, is described in a paper published in Astrobiology.
On a handful of previous Mars missions, the rovers’ life-seeking machines worked slowly—either because they had to collect samples for analysis or because they surveyed the landscape with lasers that only lit up a pinpoint of terrain at a time. The Standoff Biofinder can cover more ground because a special lens spreads its laser beam into a searchlight nearly ten inches across.
When the device showers a surface with laser light, molecules that absorb the radiation become excited and emit a faint fluorescent glow. Proteins, lipids, and other biologically produced substances only glow for a matter of nanoseconds, whereas the fluorescence given off rocks and minerals lasts thousands or millions of times longer. By recognizing only fluorescent blips less than 20 nanoseconds long, the Standoff Biofinder can pick out biological materials—dead or alive—against non-biological background materials.
A team of researchers led by Anupam Misra, a physicist at the University of Hawaii, recently put the Standoff Biofinder through the ringer to evaluate its life-perceiving prowess. In a series of lab experiments, researchers scanned various biological targets, such as crushed eggshells and algae-coated coral. The instrument was able to detect vestiges of life up to two meters (about 6.5 feet) away in one-tenth of a second. Misra was particularly impressed by the Biofinder’s ability to discern microbes among grains of Antarctic soil, which strongly resembles the Martian terrain.
“I’m really glad to see that this team has got [the Standoff Biofinder] up and running, and to see how well it performs with different examples of biological material,” said Lewis Dartnell, an astrobiologist and author of Life in the Universe: A Beginner’s Guide, who was not involved in the project.
According to Dartnell, this new gadget’s in-lab success does come with a caveat. Namely, any biological material on the surface of Mars has probably been so heavily degraded by the sun’s ultraviolet radiation that it would glow much more faintly than the organisms that Misra’s team used in their experiments. However, Dartnell said the new machine could work very well on freshly exposed material, like soil dug up from underground or rocks whose surfaces have been worn down with an abrasion tool.
Another limit to the Standoff Biofinder’s utility is that it can only recognize the presence of biological material—it can’t distinguish between different types of organisms. But this instrument could still be useful “in a triage function, scanning ahead of a Mars rover for any fluorescent signs of [life],” Dartnell said. The Standoff Biofinder would identify the most promising sites, and then other equipment on the rover could examine that terrain more closely.
Craig Marshall, a geologist at the University of Kansas who was not involved with the project, sees the instrument in a similar light. “I don’t think finding life on Mars is going to be as easy as point-and-shoot with the Standoff Biofinder within the first few minutes,” he said. “I do think it’s a good screening technique to find promising samples.”
The next step in getting the sensor to the Red Planet is building a much smaller version that would fit on a spacecraft, said Chris McKay, a planetary scientist at NASA Ames Research Center and co-investigator on the project. The current model resides on a dolly, and its fluorescence detector alone weighs over 13 pounds—about as much as a bowling ball. To send their device into space, McKay said, the team has to “shrink it down to the size of, maybe not a coffee cup, but a couple of coffee cups.”