NASA engineers have shipped an envoy, the Perseverance rover, practically 300 million miles to learn the secrets and techniques trapped within the stones of Mars. A seven-foot robotic arm is chargeable for finishing the journey, bringing a cluster of assorted mechanical eyes to see at Martian rocks from simply inches away. That shall be simply shut sufficient—researchers hope—to identify delicate carvings probably left by historical life.
One such mechanical peeper is the Planetary Instrument for X-ray Lithochemistry, or PIXL, which serves an analogous goal to the 10x hand lenses many geologists carry within the discipline. However along with magnifying, PIXL will even analyze rocks in a manner by no means earlier than carried out on Mars (and never carried out all that generally on Earth). The instrument will inform the small military of planetary scientists and astrobiologists directing it not solely exactly what a rock is fabricated from, but additionally how its composite components are organized—info important to determining the place an object got here from and whether or not primitive microbes had been concerned in its formation.
PIXL works by beaming highly effective X-rays at a rock and waiting for what X-rays come again (since atoms of various components work together with the X-rays in numerous methods). Each Mars lander since Viking within the 1970s has carried such an “X-ray fluorescence” instrument to tell apart, say, iron from copper. However PIXL applies the approach in an entire new manner.
As an alternative of pointing a thick beam at a rock and getting again a easy listing of the weather current at a single location, PIXL makes use of an X-ray beam as advantageous as a human hair to scan forwards and backwards throughout a pattern. Because it covers the grid over the course of some hours, it assembles a sequence of stackable photographs exhibiting precise preparations of practically two dozen components—reminiscent of sodium, potassium, and nickel—inside an space no greater than a postage stamp.
These “elemental maps” will assist researchers unlock every pattern’s distinctive historical past. Most rocks carry scars from indignities suffered up to now, like being skewered or buried. Understanding the distributions of supplies within the samples will assist scientists reconstruct what was occurring on Mars billions of years in the past. “Youthful issues cross older issues, and youthful issues sit on high of older issues,” says Abigail Allwood, PIXL’s principal investigator.
And generally, not less than on Earth, dwelling issues chisel inanimate issues. Allwood and her colleagues plan to make use of PIXL to seek for such carvings on Mars.
[Related: Read about how Perseverance will try to make oxygen on Mars]
The treks of earlier rovers have helped planetary scientists decide that Mars was as soon as heat sufficient and moist sufficient for organisms (as we all know them) to outlive, however it in all probability didn’t keep that manner for very lengthy. If life managed to get a toehold, it seemingly wouldn’t have had time to evolve past a particularly fundamental kind, and any traces it left behind can be equally low-key.
However in combination, communities of even the best microbes might have etched marks into Martian rocks that PIXL and different devices would possibly assist establish. On Earth, for instance, probably the most historical indicators of life aren’t fossilized our bodies, however relatively odd stone patterns often called stromatolites.
Stromatolites are the remnants of microbes that after banded collectively in skinny movies, feasting on sunrays and inadvertently shaping the sand that fell round them. As contemporary “microbial mats” grew on high of previous ones, they fashioned a stack of sheets that survived as stone lengthy after different traces of the organisms had vanished.
Researchers have little notion what motifs Martian microbes might need made, however the layered texture of stromatolites serves as a proof of idea. If PIXL’s maps of components confirmed a pile of wavy layers, that rock can be price sampling for additional examine on Earth (Perseverance will stash samples for a future mission to select up).
In reality, Allwood developed PIXL partially to decipher the cryptic messages of stromatolites right here on Earth. She was a part of a crew that investigated the oldest terrestrial stromatolites (Australian specimens relationship again 3.5 billion years), first in 2006 and once more in 2009, utilizing a business X-ray fluorescence microscope—PIXL’s grandparent.
On the time, most researchers thought the important thing to determining whether or not a stromatolite-like sample had been formed by primitive microbes or geologic forces was to scrutinize a pattern micrometer by micrometer. However to Allwood, zooming out and learning a wider patch of rock usually instructed a clearer story. “I all the time discover stepping again from an issue helps you perceive it higher,” she says.
She quickly joined NASA’s Jet Propulsion Laboratory as a postdoctoral researcher, and by 2011 was engaged on the primary PIXL prototype with a watch towards sometime sending it to Mars. The instrument had developed additional by 2016, when a crew introduced the invention of an much more archaic clustering of stromatolites in Greenland, from 3.7 billion years in the past.
However after Allwood and different colleagues used the PIXL prototype to research samples of the Greenlandic stromatolites, the microbial origin didn’t maintain up. PIXL’s evaluation confirmed that there was little distinction in how components had been distributed inside and out of doors of the supposed stromatolites. Additionally they couldn’t see any layers, or “lamination,” in any way—a certain signal that the patterns within the rocks had not been left by microbes. “Mapping with PIXL confirmed that there was not even a chemical ghost of a lamination.”
On condition that researchers spend years debating the authenticity of fossilized microbial mats right here on Earth utilizing a menagerie of devices giant and small, PIXL’s lone beam of X-rays has nearly no likelihood of discovering clear proof of previous life on Mars by itself.
A convincing case that the Purple Planet was as soon as house to microbes would require further traces of proof from Perseverance’s different varied devices, and, finally, the retrieval of probably the most promising samples for a full evaluation on Earth.
Astrobiologists will want a “wealthy tapestry of knowledge involving each in situ instrument statement and return pattern statement,” Allwood says. “There are not any smoking weapons.”