The Most Convincing Evidence Yet Of Life On Mars

Summary

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Short Wave (NPR)

Episode: The Most Convincing Evidence Yet Of Life On Mars

Date: September 12, 2025
Host: Regina Barber
Guest: Dr. Himani Kolucha (Planetary Scientist, Caltech)

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Episode Overview

This episode dives into the tantalizing new evidence of ancient life on Mars, as discovered by NASA's Perseverance rover. Host Regina Barber speaks with planetary scientist Himani Kolucha about how peculiar spots on Martian rocks could represent the closest scientists have come to finding signs of life beyond Earth. Together, they explore the journey of Martian exploration, discuss recent discoveries, and reflect on the philosophical importance of such findings.

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Key Discussion Points & Insights

Setting the Scene: Mars as an Ancient Earth Analog

• Mars in the Imagination
  Regina kicks off by noting Mars has long stirred the imaginations of scientists and the public alike.
  [00:19]

• Atmospheric Oddities
  Dr. Kolucha shares vivid details about the Martian environment:

  “Mars has blue sunsets because of the difference in atmospheres and the amount of dust and things like that. Although Mars doesn’t have those sandstorms from 'The Martian,' it has really cool dust devils.”
  — Himani Kolucha (00:32)

• Geologic Similarity to the American Southwest
  Kolucha draws analogies between Mars and the landscape of Utah, referencing its vast volcanoes and dry terrain.
  [00:53]

The Evolution of Martian Life-hunting

• Was There Life On Mars?
  The central scientific question: What kind of evidence has been found that could support ancient Martian life?
  [01:12]

• Rovers and Exploration
  An overview of how Martian rovers, especially Curiosity and Perseverance, have steadily built the case for habitability:

  “The more we learn about Mars through all of the rovers, the more it seems like ancient Earth. It had these fantastic big rivers... and lakes just like Earth that were really big. And it was this wonderfully wet and alive world.”
  — Himani Kolucha (01:22)

• Martian Surface Today
  Kolucha describes current conditions: a desolate red landscape, wind-worn rocks, a far cry from its wetter past.
  [01:51]

Building the Evidence

Past Discoveries: Curiosity Rover

• Organic Matter in Gale Crater

  “When Curiosity Rover was exploring the lake sediments of Gale Crater, it found organic matter, rich sediments. ... That was sort of the first detection of organic matter.”
  — Himani Kolucha (04:28)

• Persistence of Water Curiosity continued to find signs of long-lasting lakes, crucial for life to develop.

  “It wasn’t just water for a quick second in a lake that immediately disappeared, it was long lasting water. ... That’s what you really need for life...”
  — Himani Kolucha (05:10)

The Newest Breakthrough: Perseverance Rover's "Spots"

• Jezero Crater Discovery

  “We found these millimeter sized spots. ... Some look like poppy seeds on a bagel. Some look like small leopard spots. Some are green spots with black tendrils. And they look like something that ancient life on Earth leaves behind.”
  — Himani Kolucha (05:48)

• Why Are the Spots So Exciting?

  “The spots are the first thing we’ve seen that life may have actively made or left behind instead of just a condition that allows life to happen.”
  — Himani Kolucha (06:35)

Understanding the Spots: What Do They Mean?

• Similarities to Earth

  “So when rocks are sitting in water for a long time on Earth... they get rusty... and microbes really love eating rust. ... So the way that these spots form is that the microbes essentially eat a whole spot of rust and leave behind what we see, just like a caterpillar eating out a piece of leaf.”
  — Himani Kolucha (07:14)

• Alternative Explanations Regina points out non-biological processes (like heat) could also make spots. Kolucha agrees, but highlights why life is a more likely cause.
  [08:02]

• Distinct Characteristics Arguing for Life

  • Variety:

    “There’s so many different variations that we’re seeing, and life likes to be variable... Anything that’s not life is usually pretty homogenous.”
    — Himani Kolucha (08:28)

  • Mineral Residue:
    Particular minerals are present that Earth life also leaves behind.
    [08:47]

  • Location:

    "We interestingly find these spots across the whole river channel... the fact that they're found everywhere and in these different forms... is exciting."
    — Himani Kolucha (09:18)

  • Color:
    The presence of green in the spots indicates specific chemical changes involving iron—often associated with microbes on Earth.
    [09:44]

  • Shape:

    “These spots are not [regular crystals]. They’ve got flimsy borders and squiggly lines and all those sorts of things that point to life.”
    — Himani Kolucha (10:27)

What’s Next: The Search for Proof

• The Dream Experiment

  “There’s only one thing to do. We would collect a core of these and we’d bring them right back to Earth as soon as possible... and just see what was there.”
  — Himani Kolucha (11:03)

• What Are Scientists Hoping to See?

  "We could see the mineral shapes down to the micron, down to the nanometer... measure the isotopes..."
  — Himani Kolucha (11:30)

• Will We Find Microfossils?

  "On our luckiest day? But we might not be so lucky... because these things are so old, they tend not to preserve the microfossils. ... It’s a bit like detective work, and it’s really old detective work."
  — Himani Kolucha (12:17)

Why Does This Matter? The Human Perspective

• The Big Question

  “It’s not about Mars, really. ... It’s the concept of are we alone in the universe or not? ... It’s kind of like why poetry matters or good writing heals you and things like that. It’s the art of finding these questions is something worth living for.”
  — Himani Kolucha (12:53)

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Notable Quotes & Memorable Moments

• “Some of them look like poppy seeds on a bagel. Some of them look like small leopard spots.”
  — Himani Kolucha (05:48)

• “The spots are the first thing we’ve seen that life may have actively made or left behind.”
  — Himani Kolucha (06:35)

• “It’s kind of not about Mars, really. ... It’s the art of finding these questions is something worth living for.”
  — Himani Kolucha (12:53)

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Timestamps for Important Segments

• 00:19 | Mars as a source of fascination
• 01:22 | Mars’ watery, "alive" past
• 04:28 | Curiosity’s discovery of organic matter
• 05:48 | Perseverance finds "spots" on Martian rocks
• 07:14 | Earth analogs: how microbes make spots
• 08:28 | Why these spots look “alive”
• 09:44 | The significance of color and shape in spots
• 11:03 | The urgent desire for a Mars sample return
• 12:53 | The philosophical value of searching for life

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Conclusion

Short Wave's episode offers a quick but scientifically rich exploration of the strongest evidence yet for ancient Martian life: peculiar spots on rocks in Jezero Crater that closely resemble biosignatures seen in Earth’s rock record. While the Perseverance rover cannot provide absolute proof, the accumulating clues are enough to spark both rigorous scientific tests and philosophical wonder about our place in the universe. As Dr. Kolucha so memorably puts it, it is the search itself—and the possibility that we are not alone—that makes the investigation worthwhile.

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Transcript

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[Regina Barber]

You're listening to shortwave from npr. The planet Mars has stirred the imagination of scientists and space enthusiasts for hundreds of years.

[Himani Kolucha]

So Mars has blue sunsets because of the difference in atmospheres and the amount of dust and things like that. Although Mars doesn't have those sandstorms from the Martian, it has really cool dust devils.

[Regina Barber]

That's Himani Kolucha. She's a planetary scientist who recently completed her PhD at Caltech. And she spent a lot of time thinking about Mars.

[Himani Kolucha]

You could think of like the American Southwest as a good analog, like if you were to walk through Utah. That really reminds me of what we see from the rover and what it would feel like to walk around Mars. Occasionally in the distance you would see these giant volcanoes, like bigger than the size of Mount Everest.

[Regina Barber]

Many people, including Hamani, have wondered, was there life on Mars? And the more Mars is studied, the closer scientists get to answering that question.

[Himani Kolucha]

The more we learn about Mars through all of the rovers, the more it seems like ancient Earth. It had these fantastic big rivers flowing and big deltas flowing and lakes just like Earth that were really big. And it was this wonderfully wet and alive world.

[Regina Barber]

Using the Perseverance rover, Hamani studies the Martian surface, looking for evidence of ancient life, anything that might have lived in those rivers and deltas billions of years ago.

[Himani Kolucha]

Mars looks very different now. Whenever we get pictures back from the rover, it's always this red hued layer of dust that's on all these rocks. And they're sort of broken up by a long history of it being cold and hot and broken up and fractured. And so a lot of their original glory doesn't remain in what does remain.

[Regina Barber]

Scientists think there could be traces of what ancient life has left behind. No human has been to Mars to look for these clues, which is where rovers come in. The Perseverance rover has been roaming across the Martian landscape for more than four years. As it was driving through dried up riverbeds, it saw something on the rocks that has scientists, including Hamani, excited. Something that will get humanity the closest it has ever gotten to evidence of life on Mars. That something spots on rocks. Today on the show Life on Mars, how tiny specks on rocks could be the most convincing evidence of a once living Mars. I'm Regina Barber and you're listening to Short Wave, the science podcast from npr.

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[Regina Barber]

Okay, Hamani, it really does seem like every few months there's this new headline about life on Mars. What is the evidence that's kind of been stacking up that there most likely was life on Mars at one point?

[Himani Kolucha]

So the first was that when Curiosity Rover was exploring the lake sediments of Gale Crater, it found organic matter, rich sediments. And those are really exciting because as we know, life likes to leave behind organic matter. And obviously there's other ways for organic matter to land on Mars. It can come in through meteorites. But that was sort of the first detection of organic matter. And then the second sort of big discovery from Curiosity, I would say, is that as the rover traversed higher and higher up this mountain that it's climbing, we continued to find lake sediments and sediments that had experienced water alteration. And that sort of means that it wasn't just water for a quick second in a lake that immediately disappeared, it was long lasting water. And that's what you really need for life to actually develop, to go through all those steps of, you know, from organics to becoming a cell to actually thriving for all this time. And so long lived water is a really, really exciting discovery.

[Regina Barber]

Cool. All right, so the most recent rover, what has Perseverance found?

[Himani Kolucha]

With Perseverance Rover, we came over to Jezero Crater and it landed in 2021. And we were exploring this delta for many years. And then we sort of exited the delta and went into this ancient river channel and we found these millimeter sized spots. And the spots are really exciting because they're really Intricate features. Some of them look like poppy seeds on a bagel. Some of them look like small leopard spots. Some of them are green spots with these black tendrils. And they look like something that ancient life on Earth leaves behind. We've seen it in the rock record on Earth. So that was the most exciting recent.

[Regina Barber]

Discovery in your opinion, out of all of those, what's the strongest evidence that there was once life on Mars?

[Himani Kolucha]

The spots are definitely the most exciting discovery because the, the key difference is, you know, you can have long lived water and life doesn't have to proceed. You know, you can have organic matter. Life doesn't have to thrive in it. The spots are the first thing we've seen that life may have actively made or left behind instead of just a condition that allows life to happen.

[Regina Barber]

Okay, so Hamani, these spots, they do exist on Earth, right? And those spots came from living things. How do these spots on Earth form and what do they look like?

[Himani Kolucha]

So when rocks are sitting in water for a long time on Earth, or then exposed to air for a long time, they get rusty, just like garden tools sometimes when they're sitting out in the shed for a while. And microbes really love eating rust. It's a good food for them. And so the way that these spots form is that the microbes essentially eat a whole spot of rust and leave behind what we see, just like a caterpillar sort of eating out a piece of leaf.

[Regina Barber]

What I love this. This is very easy to visualize. Okay. But like, that's not the only way these spots could have formed on Mars. Right. There could have been other things that made these spots. They might not have formed by ancient bacteria.

[Himani Kolucha]

Yes. So in addition to ancient bacteria, sometimes you can just have organic matter laying around that when the rocks are heated up, it, you know, sort of leaves behind these spots. You can think of like steam rising through some grates and leaving behind the pattern, essentially.

[Regina Barber]

So why is this so convincing that it's not that, like, that it's not heat and it is maybe a microbe.

[Himani Kolucha]

So there's a couple different lines. One is there's so many different variations that we're seeing, and life likes to be variable and not homogenous. And, you know, anything that's not life is usually pretty homogenous. The other reason.

[Regina Barber]

Oh, okay.

[Himani Kolucha]

The other reason is that the minerals that are left behind in the spots are also things that life likes to leave behind. And so that's another way that we sort of look for ancient life is we look for specific minerals that we Know, ancient life on Earth likes to leave behind.

[Regina Barber]

Okay, so. So there are like you're telling me there's a few reasons why maybe the easiest explanation for these spots is ancient life location is one of them. Can you tell me about that?

[Himani Kolucha]

Yeah. So we interestingly find these spots across the whole river channel, which is really exciting because, you know, if they were just next to a heat source or something like that, you might be more suspicious. But the fact that they're found everywhere and in these different forms and usually life likes to leave behind intricate stuff. So the tendrils in the green spots, for example, are really intricate.

[Regina Barber]

Tell me why the color, like some of these spots are green. Why would that color be important for life?

[Himani Kolucha]

Yeah, so rusty rocks are all red. And so that's sort of the background of red that we're looking at. But you could think of how a penny starts out brown and then rusts to green. Well, iron rusts to red, but then when it's reduced back it goes to green. And so we're seeing a change in iron, but just in the little spot we're not seeing it everywh. So that points to a really specific process.

[Regina Barber]

And you had talked about these like leopard spots and like poppy seeds. So is the shape of these spots important?

[Himani Kolucha]

Yes, absolutely. Because you can think of minerals. You might have seen the gem collection at the Natural History Museum. They're very regular in their shape. They're crystals with very definite shapes. And these spots are not that. They've got flimsy borders and squiggly lines and all those sorts of things that point to life.

[Regina Barber]

Oh, that's so cool. What's the ideal next step though? Like if you hamoani had all the money in the world, what would you do next to verify that there was indeed like ancient life on Mars?

[Himani Kolucha]

Yeah, I mean, there's only one thing to do. We would collect a core of these and we'd bring them right back to Earth as soon as possible. You know, revive Mars sample return, and then put all of our laboratory instruments on them and just see what was there.

[Regina Barber]

If Mars sample return miraculously happens and we get these cores back, what would we have to see in that microscope to tell us? Yes, there was ancient life on Mars.

[Himani Kolucha]

Yeah. So with the rover, we can see pretty small things, we can see millimeter sized things, but with our microscopes on Earth we can see micron sized things, nanometer sized things. And so we could see the mineral shapes down to the micron, down to the nanometer, and we could see the organic matter that's maybe trapped within there, and the type of molecules that would be in there would tell us something. We could measure the isotopes of these minerals to really accurate degrees and see if they point to something life has made. There's a whole host of tests that we could do.

[Regina Barber]

Would is it possible that we would actually see an organism like a fossil.

[Himani Kolucha]

On our luckiest day? But we might not be so lucky, you know, because these things are so old, they tend not to preserve the microfossils. And even on Earth, these types of spots don't tend to preserve microfossils. Okay, got it. So, yeah, we have to look for other signs. And it's a bit like detective work, and it's really old detective work, so it's not always clear, but it's worth trying.

[Regina Barber]

Why does it matter that maybe there was life once on Mars?

[Himani Kolucha]

I was actually at a wedding recently and I was asked the same thing. So I feel I'm prepared for this. It's kind of not about Mars, really. It's not about one specific place. It's the concept of are we alone in the universe or not? And you could say, well, you know, that doesn't affect my taxes and it doesn't really change anything about my day to day life. But it's kind of like why poetry matters or good writing heals you and things like that. It's the art of finding these questions is something worth living for.

[Regina Barber]

Hamani, thank you so much for talking with us today about the possibility that there was life on Mars.

[Himani Kolucha]

Anytime. It's my favorite thing.

[Regina Barber]

If you liked this episode, follow us on the NPR app or whatever podcasting platform you use. And if you have an idea for a space or honestly, any other science story we haven't covered, email us your [e-mail] this episode was produced by Burleigh McCoy, edited by Megan Cain, and fact checked by Tyler Jones. Kwesi Lee was the audio engineer, Beth Donovan is our senior director, and Colin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber. Thank you for listening to short wave from NPR.

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