It all happened so fast! On Thursday, February 18th, NASA’s Perseverance rover set landed in the Jezero crater on Mars and almost immediately transmitted its first image of the Martian. This was followed by photos from the Mars Reconnaissance Orbiter and footage taken by the rover’s Entry, Descent, and Landing (EDL). Then there was the panoramic video, a sound recording, and deployed its Ingenuity helicopter, all in the space of a week!
But that’s nothing compared to what happened next. Shortly after the rover started drilling into the floor of the Jezero crater, Perseverance found evidence of fossilized bacteria! The search for life on Mars finally struck paydirt! Okay, that didn’t happen… Not yet, anyway. But what if it does? After all, one of Perseverance‘s main objectives is to search for evidence of past life on Mars. What will be the impact if and when it finds it?
The Perseverance rover is NASA’s ninth mission to land on Mars and (like its predecessors) is tasked with characterizing the geology, atmosphere, and climate of Mars and help pave the way for human exploration. But the rover is also focused on astrobiology, which refers to the study of life throughout the Universe. As the next most-habitable place in our Solar System beyond Earth, Mars is a major focus of our astrobiological efforts.
As Gentry Lee, the chief engineer for the Planetary Science Directorate at NASA’s Jet Propulsion Laboratory, explained in a JPL press release:
“To quote Carl Sagan, ‘If we see a hedgehog staring in the camera, we would know there’s current and certainly ancient life on Mars, but based on our past experiences, such an event is extremely unlikely. Extraordinary claims require extraordinary evidence, and the discovery that life existed elsewhere in the universe would certainly be extraordinary.'”
Thanks to the many rovers, orbiters, and landers that explored Mars in the past, scientists understand that billions of years ago, Mars was a much different place than it is today. Its atmosphere was denser, its climate warmer, and liquid water flowed on its surface. This led to many of the features that are observable today, like the preserved river delta in the Jezero crater.
This feature indicates that ca. 3.5 billion years ago, Jezero was a lakebed that had water flowing into it. This caused sediment to build up over time, leading to the formation of a river delta that is rich in clays. While the lake may be long gone, scientists theorize that there could be biosignatures somewhere in this 45 km (28 mi) wide crater just waiting to be found.
Given the relatively brief window Mars had for habitability, odds are that only simple lifeforms (like single-celled bacteria) would have emerged. On Earth, some of the most ancient evidence for life comes in the form of microbialites, sedimentary deposits composed of carbonate mud that form with the help of photosynthetic cyanobacteria.
Said Ken Williford, the deputy project scientist for the Perseverance mission:
“We expect the best places to look for biosignatures would be in Jezero’s lakebed or in shoreline sediments that could be encrusted with carbonate minerals, which are especially good at preserving certain kinds of fossilized life on Earth. But as we search for evidence of ancient microbes on an ancient alien world, it’s important to keep an open mind.”
Tools of the Trade
Using its advanced suite of scientific instruments, Perseverance will collect rock core samples in metal tubes and place them in a supply cache (which will be retrieved by a future mission sent by the ESA). These instruments include the rover’s suite of cameras, especially the one located on the rover’s mast that’s capable of zooming in to inspect targets (Mastcam-Z).
There’s also the SuperCam instrument, which is also located on the mast and can use a small laser to examine promising research targets. This is done by using the laser to create small clouds of plasma clouds, which will then be analyzed to determine the target’s chemical composition. If the data it obtains reveals something interesting, the rover will be able to examine it more closely with its two turret-mounted instruments.
These are known as the Planetary Instrument for X-ray Lithochemistry (PIXL) and the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) instruments. The former relies on small x-ray bursts to search for chemical biosignatures while the latter uses its own laser to detect concentrations of organic molecules and minerals that have been formed in watery environments.
Together, these two instruments will effectively create high-resolution maps of elements, minerals, and molecules in Martian rocks and sediments, which astrobiologists will use to determine which to collect and eventually send back to Earth. As Bobby Braun, the Mars Sample Return program manager at JPL, explained:
“The instrumentation required to definitively prove microbial life once existed on Mars is too large and complex to bring to Mars. That is why NASA is partnering with the European Space Agency on a multi-mission effort, called Mars Sample Return, to retrieve the samples Perseverance collects and bring them back to Earth for study in laboratories across the globe.”
“We have strong evidence that Jezero Crater once had the ingredients for life. Even if we conclude after returned sample analysis that the lake was uninhabited, we will have learned something important about the reach of life in the cosmos,” said Williford. “Whether or not Mars was ever a living planet, it’s essential to understand how rocky planets like ours form and evolve. Why did our own planet remain hospitable as Mars became a desolate wasteland?”
In short, the Perseverance mission is dedicated to the search for life and is equipped with the very best that modern science can offer. So it naturally begs the question, what happens if and when it succeeds?
Well for starters, the announcement would spread around the world like wildfire. Just imagine the headlines: “Perseverance finds evidence of Martian life!” “Humanity discovers extraterrestrial bacteria!” The excitement would be palpable and would be felt wherever the news reached. Of course, it would also raise some very important questions, the answers to which would have some rather drastic implications.
First of all, there’s the question of whether or not life on Mars is related to life on Earth. If the answer to this question is yes, then scientists would have solid evidence of lithopanspermia, where life is distributed between planets in a star system. Alternately, it could be an indication of panspermia, where life is distributed throughout the cosmos by celestial bodies like asteroids and comets.
In this case, it could be argued that Earth and Mars were seeded from the same source (though that would be extremely difficult to prove). Dr. Tanja Bosak, a professor of geobiology at MIT and the group leader of their Program in Geology, Geochemistry and Geobiology, is also the Returned Sample Science Lead for the NASA Mars 2020 Perseverance mission. As she told Universe Today via email:
“The most direct test of the genetic relatedness of any martian and terrestrial life would come from the comparisons of the information molecules (DNA, RNA) and the presence of such molecules in anything we find... In the best-case scenario, we’d find fossils of microbes or some such biosignature, but DNA and RNA do not preserve over billions of years, i.e., from the time when surface life was possible in Jezero crater. However, if we see something that looks like fossil cells upon sample return, and detect some organic biosignatures, that would automatically support the similarities between past life on Mars and life on Earth.”
Second, the discovery of evidence for past life on Mars is likely to lend some credibility to the theory that life still exists there today. Much like the disappearance of Mars’ surface water, it is theorized that microbial life could have also migrated underground as a result of changes in the planet’s climate. In fact, research has been conducted that demonstrated how microbes could survive beneath the surface in briny patches of water.
As Dr. Bosak added, the scientific consensus is that modern surface life on Mars is highly unlikely, hence why Perseverance aims to collect samples that will preserve evidence of past life. Nevertheless, the existence of past life will make the issue of planetary protection all the more pressing when crewed missions to Mars commences, especially if they lead to an enduring human presence there.
Already, robotic missions are forced to exercise care in the vicinity of potential sites for microbial life, a good example of which is the time Curiosity came upon a discolored patch of sand (thought to be a surface brine) and was forced to divert its path to go around it. If human habitats are ever built on Mars (either temporary or permanent), the possibility that we could be causing harm to Martian organisms will always be there.
The Perseverance rover will not provide the final word on this subject, but the data it collects and the sample return it will perform will provide an essential piece to the puzzle. After all, the search for life on Mars is like the search for meaning in the Universe: ongoing! And while we’re waiting for answers, here’s some entirely appropriate music to help us pass the time. Take it away David Bowie!
Further Reading: NASA