Space News Deep Dive: Life on Mars? Not Quite.

Article September 24, 2025

I know this news is a couple of weeks old at this point, but that doesn’t seem like a reason not to dive into what may turn out to be some of the most consequential news ever to come off of the Red Planet (or, you know, could also turn out to be some pretty dots on a rock). Earlier this month NASA announced that the Perseverance rover had discovered a potential biosignature on the planet Mars.

Now just so we are quite clear right from the start, what Perseverance did not find was proof of either current or past life on Mars. However what it did find is awfully intriguing and has the possibility of one day proving to be the first step on the road to that very discovery. So let’s take a swing out to Mars and find out what Perseverance is doing and what all the hubbub is about.

The Perseverance rover (which is capable of taking pictures of itself) in Jezero Crater on the surface of Mars. Credit: NASA
The Perseverance rover (which is capable of taking pictures of itself) in Jezero Crater on the surface of Mars. Credit: NASA”

 

Some Quick Background

Just in case you don’t know, Perseverance is the name of NASA’s largest and most state-of-the-art Mars rover, which landed in Jezero Crater on the Red Planet in February 2021. Jezero was chosen as a prime landing site because it is believed to have once held a Martian lake, and to have held both the right environment for supporting life, once upon a time, as well as the sorts of sedimentary rocks that are good at preserving evidence of any such life.

The “leopard spots” seen on the rock known as Chevaya Falls on Mars. Credit: NASA
The “leopard spots” seen on the rock known as Chevaya Falls on Mars. Credit: NASA

Perseverance spent over three years exploring the crater’s bottom before beginning a slow and careful climb to the rim. Along the way it passed a river valley named Neretva Vallis, which held a set of rocky outcrops that were nicknamed the Bright Angel formation. While taking a closer look at Bright Angel, Perseverance happened upon a particularly intriguing rock, which received the name Chevaya Falls.

In summer 2024 Chevaya Falls made a lot of news for being covered in spots, visible in the images Perseverance has sent to Earth. These spots, irregular light patches with dark rings, were nicknamed “leopard spots” and caught everyone’s attention for resembling not only the fabulous coats of big Earth cats but also spots that we find in sedimentary rocks here at home. When we see them here, they can be an indication of microscopic life, so naturally everyone was very curious about what was going on with those Martian leopard spots.

 

A Closer Look

There was, of course, no question but that Perseverance would be taking a closer look at Chevaya Falls and its spots. And now we know what came of that closer look, just what it is Perseverance discovered lurking in the crevices of Chevaya Falls. Namely vivianite and greigite.

Images taken from Mars orbiters and from Perseverance on the ground showing the location of the Bright Angel formation. Credit: NASA/JPL-Caltech/ASU/MSSS
Images taken from Mars orbiters and from Perseverance on the ground showing the location of the Bright Angel formation. Credit: NASA/JPL-Caltech/ASU/MSSS

If that doesn’t get your heart pumping, don’t feel bad—I had no idea what this stuff was either until I read up more. Vivianite and greigite are both iron-rich minerals (specifically hydrated iron sulphite and iron sulfide). They form from electron transfer reactions that happen between sediment and organic matter—and note that organic matter does not mean organisms, it means carbon-rich material.

That’s exciting because this is exactly the kind of byproduct you’d see from a microbe using these electron transfer reactions to produce energy. We see electron transfer processes happen on Earth, it’s part of photosynthesis. And we know the Bright Angel formation includes all kinds of chemicals that could make a microbe happy.

In short, we have an environment we think is capable of supporting microbial life peppered with minerals that microbial life can create as a part of their life process. So why exactly are we not singing to the stars that we’ve found evidence for past life on Mars? There are, naturally, some complications to be taken into account.

 

No Biology Required?

The CoLD Scale is one metric scientists use when determining how well evidence supports the idea of the presence of life. Perseverance’s recent discovery ranks at about Level 3. Credit: NASA
The CoLD Scale is one metric scientists use when determining how well evidence supports the idea of the presence of life. Perseverance’s recent discovery ranks at about Level 3. Credit: NASA

Microbes do create vivianite and greigite. But they’re not the only things that can do so. It is quite possible to create these exact same minerals without a single biological process involved. In order to say for certain that we have absolutely found a biosignature, evidence left behind by a living organism, on Mars, we’d need to be able to rule out the possibility of these minerals being produced abiotically. And right now we can’t.

BUT. It looks like we can probably rule out the most likely ways that these minerals could be created without a helpful bacteria around. When vivianite and greigite are formed outside of the presence of life, it takes certain very specific conditions, including very high temperatures and a highly acidic environment.

High temps and a lot of acid tend to leave their marks on rocks. The Bright Angel formation, including Chevaya Falls, shows no signs of having been through the kind of hot, acidic conditions that would, we think, have been required to make the vivianite and greigite abiotically. If it’s possible for these minerals to be made in lower temp, lower acidity environments, we don’t know about it. 

That still doesn’t mean we can start crowing. Extraordinary claims require the most extraordinary evidence, and that includes either definitively ruling out every single possible abiotic source for these minerals or finding a way to prove conclusively that it was a microbe that made them. And Perseverance simply cannot do that.

 

Heading Home

Image from Perseverance showing the spot where the sample Sapphire Canyon was taken from the rock known as Chevaya Falls. It also highlights two sites where Perseverance made abrasions in the rock to study further. Since everything on Mars has a name, these abrasions are named Steamboat Mountain and Apollo Temple. Credit: NASA/JPL-Caltech/ASU/MSSS
Image from Perseverance showing the spot where the sample Sapphire Canyon was taken from the rock known as Chevaya Falls. It also highlights two sites where Perseverance made abrasions in the rock to study further. Since everything on Mars has a name, these abrasions are named Steamboat Mountain and Apollo Temple. Credit: NASA/JPL-Caltech/ASU/MSSS

Look, Perseverance is fantastic. It’s a semi-autonomous mobile science laboratory absolutely bristling with cameras and instruments operating in a place where the cold tries to freeze your gears, the sandpits could ensare you forever, and the rocks chew your wheels apart. Perseverance is amazing. But there is a limit to what it can do. It has reached that limit with Chevaya Falls.

If we want to be able to say for certain that Chevaya Falls’ spots were not made abiotically, it will take an Earth-based laboratory to do it. Fortunately the very first step of that process has already been achieved. In July 2024 the rover collected a sample from Chevaya Falls. It’s the 25th such sample it has collected, each with its own nickname because a rover can’t turn over a pebble on Mars without someone giving that pebble a name. This sample’s name is Sapphire Canyon. 

These sample tubes are meant, sometime in the future, to be collected and returned home by the Mars Sample Return (MSR) mission. And that’s where we hit a big (huge) snag. Getting MSR built has been…a problem. Over the years it has experienced several massive redesigns which has meant huge scheduling delays and a truly, horrifically, eye-wateringly high budget overrun.

An early infographic explaining how the Mars Sample Return mission would work. You’ll notice that it looks…complicated. Credit: ESA
An early infographic explaining how the Mars Sample Return mission would work. You’ll notice that it looks…complicated. Credit: ESA

All of this has led to MSR being on the chopping block, or at least lurking uneasily in its vicinity, for the last several years. At this point it’s still technically being kept alive by a slow drip-drip of funding each year, enough to stop it from being completely cancelled but not really enough to get development ramping up. And if and when development does ever ramp up nobody knows right now what that will look like as NASA seeks to find a leaner, cheaper alternative to the original, impossibly expensive mission design.

At this point it remains to be seen whether MSR will ever actually make it off the ground. But perhaps the existence of Sapphire Canyon, resting in the fine red dust of Mars, possibly containing the answer to the question that has teased at humanity since we first looked up at the stars and realized there were other worlds out there, just waiting to be picked up, is the impetus that will start the ball rolling again.

Perhaps Sapphire Canyon will be returned to Earth. And maybe, just maybe mind you, we’ll find out that life is definitely possible on other worlds. I don’t know about you, but I’ll be keeping my fingers crossed.