On the floor of a shallow crater on Mars, the NASA rover Perseverance has hit what scientists are hoping is pay dirt. Martian rocks excavated by the rover show signs of a watery past and are loaded with the kind of organic molecules that are the foundation for life as we know it.
Scientists collaborating on the mission also say the rock samples, which the rover has cached in tubes for a future return to Earth, have the right chemical recipe to preserve evidence of ancient Martian life, if it ever existed.
The new Perseverance research is detailed in three extensive studies, one in the journal Science and two in the journal Science Advances. The journal reports are highly technical and devoid of hype – daring to be dull as dirt – but the scientists involved translate them into a more exciting tale.
One of the studies concluded that the rocks in the crater experienced three different events in which they were exposed to water.
Perseverance made a bulls-eye landing in Jezero Crater on Feb. 18, 2021, and has been roaming it since, caching rock samples along the way for later scrutiny back on Earth. This is an ambitious, multiphase mission that will require NASA to send another vehicle to the surface of Mars with the capability of launching samples into orbit. A spacecraft would then carry those samples back to Earth for laboratory research. The precise timetable is still to be determined, but NASA is hoping to have the samples on home turf in the early 2030s.
This study of Mars is part of the efflorescence of the young field of astrobiology, which includes the search for potentially habitable worlds and the first example of extraterrestrial life. Despite the efforts of generations of scientists, and notwithstanding the claims of UFO buffs, the discovery of life beyond Earth remains aspirational.
Even finding organics – life-friendly molecules with combinations of carbon, hydrogen and oxygen – is a far cry from discovering life or even proof of its presence in the past. Such molecules can be either biological or non-biological in origin.
Still, Mars is front and center in NASA’s search because it has many favorable traits. Mars probably was far more Earthlike about 3 billion years ago, with warmer and wetter conditions. Life may have once existed on Earth and Mars simultaneously, and it is possible that it originated on Mars and spread to Earth via meteorites. And though the surface now is an arid wasteland, the planet could have liquid water in significant quantities beneath the surface, and possibly “cryptic” life.
All of this is an attempt to solve the fundamental mystery of Mars: What went wrong? How and when and why did this planet that apparently was congenial to life turn into such a harsh place? The Red Planet may not be a dead planet – the coroner’s report is incomplete – but it certainly resembles one.
Scientists point to something Mars lacks today: a global magnetic field like Earth’s. Such a field protects our atmosphere from the corrosive effects of the solar wind – high-energy particles steadily streaming from the sun that can strip away lighter molecules. Mars also lacks plate tectonics, the geological process that on Earth recycles the crust and continues to spew water and nutrient-rich lavas through active volcanoes.
Somewhere along the way, Mars’s magnetic field died, and then it became a different kind of planet. It lost almost all of its atmosphere. It became a frigid desert world. How quickly that happened is unknown, but that’s something that might be revealed by the volcanic rocks in the crater.
Once the mission can send its precious rock collection back to Earth, scientists may finally be able to tell if life ever found a foothold on Mars – which would raise new questions about whether, despite the dramatic transformation of the planet, life somehow managed to persevere.