The material found on Martian rocks, Murphy’s team warns, might have originated from non-biological processes as well.
A result like this usually invites two major questions, and the team immediately got busy trying to answer them.
Artifacts and stowaways
The first concern was that the signal could have been light bouncing off SHERLOC’s own fused-silica front window. Bright Angel was the first site SHERLOC examined after a dust-cover anomaly disabled its focusing mechanism, forcing the team to adopt a new operating mode.
To characterize the new mode, Kyle Uckert, SHERLOC’s deputy principal investigator at NASA’s JPL, and his colleagues collected spectra from spare flight optics in their own lab. They also pointed SHERLOC at nothing in particular on Mars and at known calibration targets. All these were used to confirm that SHERLOC was working properly.
The final confirmation of the data came when the team pointed it at Steamboat Mountain. “Other rock targets nearby do not exhibit the G-band spectral signal,” Uckert said. The Bright Angel signal was not coming from hardware.
The second concern was contamination—perhaps the rover itself dragged the organic material from Earth? Scientists pointed out that the abrasion bit the rover used to expose the rocks was sterilized before launch and has cut into other rocks across Jezero without ever producing a G-band this strong.
Also, the Cheyava Falls rock was never touched by the hardware; the rover just blew the dust off its surface with a nitrogen puff. On top of that, the Steamboat Mountain scientist used as a control again came up empty. “It did not exhibit spectral evidence of organic matter,” Uckert explained.
Chemical company
Once it was clear that the finding was most likely real, the team took a closer look at the chemistry of the material nearest to the Martian macromolecular carbon. “It suggests the carbon emplacement may have occurred during at least two different events over geologic time,” Murphy said.
At Apollo Temple, the signal clustered with carbonate and sulfate minerals–the kind that precipitate out of water moving through older rock. At Walhalla Glades, the carbon instead sat within silicate-rich sediment.
