In this episode, we are joined by Dr Joby Hollis who is part of the science team of the NASA Perseverance rover to tackle the question of life on the Red Planet, and what to expect from Perseverance when it lands on Mars in 2021. 

Listen on Apple Podcast or on your favourite podcast player through Anchor.

Chris
Welcome to a brand new episode of The Astroholic Explains! Today we have a pretty cool episode and we have an extra special guest. extra special guests Please introduce yourself.

Joby
Hi, I’m Dr. Joby Razzell Hollis

Alfredo Carpineti
Hi Joby.

Chris
Hey, Joby! Please tell us a little bit about what you do.

Joby
Okay, so I’m a NASA postdoctoral fellow at the Jet Propulsion Laboratory in California. And I’m on the science team for the Mars 2020 mission [now called Perseverance] , which will be landing on Mars in early 2021.

Alfredo Carpineti
That’s very exciting.

Chris
That’s super exciting. So, one big question, I’m going to ask you to kick this whole thing off today. Is there life on Mars?

Alfredo Carpineti
You need to take it because I’m dealing with a very much David Bowie approach.

Chris
I was expecting you to sing that

Joby
Spiders on Mars

Alfredo Carpineti
Well, spiders Mars! Lichens on Mars. There’s everything on Mars.

Joby
The short answer is we don’t know yet.

Chris
What’s the long answer?

Joby
The long answer is that Mars is actually a far more inhospitable place than we believed, say 100 years ago. Certainly, when we first started turning telescopes towards Mars, and we saw, for example, Vallis Marineris, the massive canyons on the surface of Mars. Early astronomers believed that they were canals and that the planet had been irrigated by some kind of sentient life form. That’s where the whole like, you know, War of the World-style aliens, Martians, that’s where that concept began. But obviously, since we’ve actually visited Mars with robotic spacecraft and landers, one of the things we’ve discovered is that Mars is a very, very unpleasant place now. Imagine the most inhospitable part of Earth, and it will still be so much nicer than the nicest part of Mars, basically, because at least you can breathe the air on Earth. On Mars, there’s very little atmosphere, there’s a lot of radiation, there’s very little water that we can find. And when there is water, it is generally tied up in ice, deep underground. We’ve explored Mars far more than we’ve ever explored any other world beyond Earth. But unfortunately what that means is that we have sent a couple of satellite missions. So satellites orbiting the red planet as well as eight or nine landers. And those landers have sampled specific locations on the surface and we have not found conclusive evidence either way that there are living things present there now.

Alfredo Carpineti
I just wanted to add that you can sort of blames the Italians for the misconception about Mars because astronomer Giovanni Schiaparelli is the one that first saw Valles Marineris and he called it, in Italian, a canale, but in Italian, it means both channel and canal. So when it was translated… we sort of pretty much put forward the idea that there were little green men.

Joby
Well, I think the the idea of life on what appeared to be Earth’s sister world was very appealing to start with, I don’t think they needed much incentive to, to conclude that there must be aliens because there were lines on a planet.

Alfredo Carpineti
To be honest, you’re right. There was also something similar when the first exploration of Venus came up, because there were so many clouds and we couldn’t see the surface. It was so exciting! What kind of people could live there! And well, things that Mars is inhospitable. Venus is a hellscape!

Joby
Well, the current understanding of Martian history is that for about a billion years or so, early Earth and early Mars were very similar worlds they were hot and wet. They both had magnetic fields. And it was around the same time that life evolved on earth. Like the most simple like microbial single cell life evolved about three and a half billion years ago. And we believe that is possible the conditions on Mars were similar enough that that could have happened there. So we don’t think we have we can’t discount the possibility that there was life. However, we have not yet found evidence, chemical or physical evidence that there was that life on the surface that we’ve explored so far. But if you imagine like, if you were to sample eight random locations on Earth, you probably wouldn’t be able to infer the existence of human beings. So you know, it’s worth understanding that’s a very small sample size when you spread it across a whole world. Now, the really big challenge with Mars is, yeah, if early Earth and early Mars were very similar, well, how did they diverge. And so earth as we know it today, it was hot and wet back then, and it’s still pretty warm and wet. Now we have a lot of liquid water on the surface of the earth. We still have a good, thick atmosphere for full of moisture, and we have a magnetic field so the planets still warm and wet, really. And that’s what as far as we know, what life likes. Mars is a lot smaller than Earth, so Mars cooled down a lot faster than Earth did. And as it cooled down the magnetic field shut down because the the molten metal core of the planet solidified. So you don’t have that dynamo effect that creates a magnetic field that shields the planet from radiation. And without that shield, the atmosphere started getting stripped away by the solar wind. So as the atmosphere faded away over the next billion years or so, the planet got colder and colder and colder, and then all the liquid water froze and ended up deep underground. So right now the current surface of Mars even though we can see evidence of these channels like Valles Mariners, we can see what were ancient riverbeds and deltas, so we know that liquid water once flowed on the surface of Mars. But now it’s more arid than the deserts you find on Earth.

Chris
Wow. Wow.

Alfredo Carpineti
I’m really feeling that it’s time for an intervention on Mars. Like when did it all go wrong? You were doing so well. What happened?

Chris
In terms of the ice that’s deep underground now and on on Mars… I know that there is… Is it a little mole? a robot that’s digging on Mars?

Joby
You’re referring to The Mole on InSight?

Chris
Yeah.

Alfredo Carpineti
It’s not digging for ice

Joby
It’s a thermal probe. So it’s studying the temperature changes as you go deeper into the soil. So one of the interesting things is, even though we’ve sent multiple missions successfully landed on the surface of Mars, we’ve never actually explored more than a few centimeters into the Martian surface. And it’s probably because it’s very difficult sending a big drill to another planet expecting it to work. So the the mole was one of the instruments that was put aboard the NASA InSight lander that landed earlier in 2019 and Unfortunately, they hit a snag very, very early on. They managed to drill down a few centimeters and it lost traction. And it’s quite remarkable the efforts been made to try to read like dirt they pulled the probe out and they’ve tried to like it was originally designed to only go down once and not come back up. But you know, NASA engineers are determined if anything else and they’ve been trying to find ways to get the Mole to regain traction and start digging again, mostly by like holding the the landers scoop against the side of the mole to give them something to push against so that can dig back down into the sand.

Alfredo Carpineti
You can check out the video online there are quite cute in a way that we have to come up with creative solution like: modern problems require ancient solution. They’re literally holding it down so it can dig and it’s all about not knowing exactly what they were going to find. And it’s both fascinating, but also really a testament for the engineers at NASA and I think, with the DLR in Germany.

Joby
I’m afraid I don’t know.

Alfredo Carpineti
But yeah, it’s brilliant. It’s just people finding new solutions.

Chris
I’m not mistaken either. The insight has recorded the sound of Mars quakes

Joby
It has, yeah! So the one of the other instruments aboard InSight is a seismograph that has detected the first marsquakes which is incredible because it this is a planet that as far as we know is tectonically inactive so it doesn’t have plates anymore. Partly because the planets too cold. You know, you need a thin crust and a hot mantle to drive plate tectonics. Mars has not had that in billions of years. However, there is still enough strain being put on the rock on the surface of Mars to create marsquakes that we can detect. And that’s, that’s incredibly exciting because we can infer a lot about the structure of the planet like the interior structure from the from things like how these seismic waves propagate.

Alfredo Carpineti
In late December, they announced that they actually been able to follow a couple of the biggest earthquakes, well, not earthquakes marsquakes all the way to their origin point. And they hope to now combine that with satellite observations and see if there are changes on the surface like a boulder rolling maybe. And it’s super exciting!

Chris
Wow! Literally analyzing it from underground and from space!

Alfredo Carpineti
Sort of underground because it records something that happened on the ground. And so yes, it’s very exciting.

Chris
Earlier you mentioned as well that there was about seven or eight landers/rovers on Mars.

Joby
I can’t remember the exact number, but it’s around eight or nine have successfully landed over the last 40 to 50 years.

Chris
I see I had no idea they went back that far

Joby
Oh, yeah, so the first successful landers on Mars with the Viking probes that landed in the 70s. And they were the first experiments we ever did on another planet, at least another planet surface. And we’re still actually analyzing and reinterpreting the data that they collected in the context of the measurements we’ve done more recently.

Chris
Oh, that’s clever.

Joby
So that’s a great a great example of that, that the Viking landers in the 70s had these biological experiments on boards that were designed to detect organic compounds over the very first attempt to see if we could find the chemical signs of life on Mars. And unfortunately, the results were inconclusive, partly because one of the things they found was that all the compounds were chlorinated, and they didn’t understand it at the time, and they just conclude there was contamination from within the instrument itself. However, the Phoenix lander and the Curiosity rover have since discovered the origin of that chlorination. So the current understanding is that the instruments that they were using use a technique called: pyrolysis. So in order to extract the organic material from the soil, and in this case organic just It doesn’t mean like organic is in like, you know, pesticide-free kind of biological material like apples or potatoes. What it what do we mean is that the chemical context is anything that’s got a backbone of carbon atoms and contains potentially hydrogen and oxygen, nitrogen. These are like the elemental building blocks of life as we know it. So they use a technique called pyrolysis to extract the organic material from the soil. And that basically is: you heat up the soil and you detect the fragments of molecules as they come off that hot rock. But unfortunately, a lot of Martian soil contains a chemical compound called perchlorate. This is a chlorine oxygen molecule that breaks down at high temperatures and releases chlorine atoms that will then attack and damage organic molecules nearby. So unfortunately, if you try to extract organic material in the presence that using heat in the presence of perchlorate, you end up with a lot of chlorinated compounds that may not have been chlorinated in the first place. So that’s made it much more difficult for our interpretation. But it does mean that we can go back to those Viking measurements done in the 70s and go: “Oh, that’s why they were chlorinated”, so we can still reinterpret those results based on the context that we have now.

Alfredo Carpineti
That is fantastic. Absolutely fantastic that we know that!

Joby
Well, there’s still some disagreement about exactly whether the extent of chlorination was present before pyrolysis, but unfortunately, the issue here is that we cannot confirm or deny what that was because it’s been obscured by the subsequent chlorination during pyrolysis

Chris
with the pyrolysis like, pre-Viking landers, would that have had a big effect on why Mars is currently so arid with that process have actually contributed towards destroying biological life on Mars and breaking it down?

Joby
Well, partly that yes, I mean, certainly perchlorate is toxic to terrestrial life, life here on earth. And you wouldn’t want to be growing vegetables in soil contained 1% by weight perchlorate Trust me. So we know it’s certainly not amenable to life. But in this case, it was the combination of heat and perchlorate that was so damaging. We have to recognize that without a thick atmosphere, without an ozone layer, and without a magnetic field, Mars is a very irradiated environment. There’s a lot of harsh ultraviolet from the sun, solar wind, cosmic rays. Its surface is a fairly unpleasant place. And a lot of that radiation will damage organic material like DNA, break it, and break it down. It will be basically the worst sunburn you could imagine. So certainly, right now, as it stands, you wouldn’t want to be on the surface of Mars without a good spacesuit, not just because of the cold not just because of the weak atmosphere, but also because of the radiation and that radiation will be a hazard to any living thing on the surface. Unfortunately, some experiments have shown that if you treat a fairly radiation resistant bacterium such as cyanobacteria, to Martian levels of ultraviolet, you can sterilize it within about half an hour. Cyanobacteria are like the kind of basic bacteria that absorbs sunlight and turn it into chemical energy. And you can kill them all within an hour or so. So it’s a pretty unpleasant environment, which is why a lot of the questions about potential life on Mars, whether it’s present now or if it existed in the past, we are looking more and more at the subsurface. Because ultraviolet light doesn’t penetrate very far, maybe a couple of millimeters to a half a centimeter into most rock. So, so if you can get deep enough below the surface, you’ll be protected from that radiation. And what’s more, the deeper into the ground you go, the warmer it gets. There’s no possibility of liquid water on the surface of Mars under the current conditions that we can observe. And while there may have been liquid water in the past, it’s possible that there is still liquid water on Mars, but it’s simply hundreds of meters below the surface where the pressure creates a higher temperature. So there could be a habitable region on Mars that has nothing to do with where you are with respect to the equator, but could be dependent on how deep into the planet you go. One of the mission goals of the Mole instrument on InSight is to establish the thermal gradients that you observe as you go below the surface. And of course, if the radiation dose you get goes down, you might find that habitable zone where it’s warm enough liquid water, and the radiation levels are low enough that some molecules could have organized together to form a self replicating organism.

Chris
Wow.

Alfredo Carpineti
I’m now picturing a sort of underground water park for Martians

Chris
Hollow Mars theory.

Alfredo Carpineti
I like it.

Joby
I feel like I should nip that in the bud before it gets out.

Alfredo Carpineti
So, since we’ve been talking about the exploration, do you want to tell us a little bit about your work?

Joby
Yeah, definitely. So I’m on the science team for Mars 2020, but more specifically, I work on one instrument that’s going aboard the Mars 2020 rover (Perseverance). The instrument is called SHERLOC and like everything at NASA is an acronym. It stands for Scanning Habitable Environments using Raman and Luminescence of Organics and Chemicals.

Chris
Love it!

Joby
Yeah, it’s fantastic.

Alfredo Carpineti
That’s one of my favourite of backronym. Like for me, the top is still BOOMERANG, which is a mission to study the cosmic microwave background and cannot remember the acronym but it was a mission that would circle the Antarctic and then come back to the same place. So that was genius, but I love SHERLOC. It’s very good.

Joby
It’s even better than you think. So the Sherlock instrument is attached to a Wide Field Camera called WATSON.

Chris
Oh, I love it.

Joby
So yes, SHERLOC and WATSON are built together. They are mounted onto the the end of the arm of the rover. So whenever the rover finds a rock or a surface of interest. If we think there’s some particularly interesting mineral strata there, or we think we may have found, for example, clay that could contain organic material because it came from an ancient riverbed. What we can do is we extend the rover’s arm to hold the SHERLOC and WATSON instruments over the surface in question. And we can take a picture with WATSON. And then we scan the surface with SHERLOC. So SHERLOC uses an ultraviolet laser scattered across the sample, we look at the light that gets scattered back. Some of that light will be what’s called fluorescence. So that’s light that’s been absorbed by molecules in the rock. And then those molecules have released that light at different wavelengths. And for example, biological molecules like DNA, protein, these all have very distinctive fluorescence features that we will be able to identify. What’s more, we also get this thing called Raman scattering, which is basically like a fingerprint of a molecule. What happens is when the light bounces off these molecules, there’s a chance you can excite what they call atomic vibrations. So imagine the actual molecular structure is starting to vibrate in a certain way. And that creates a very distinctive pattern of peaks that we observe. And basically it’s so specific to that molecule structure there is effectively a fingerprint. So we’re able to use this instrument to non destructively scan, a surface looking for complicated organic molecules that could be the building blocks of life. And we’ll be able to not just detect them, but also identify them, and build up a picture of what minerals are associated with and how they could have been deposited. And when. And the whole idea is we’re looking for the building blocks of life. So for example, life as we know it on Earth has four bases of DNA, and roughly 22 amino acids that make up proteins. You know, in the most simple terms, those are the building blocks of life on Earth. Now, we don’t know what the building blocks of life would be on another planet. It could be a completely different set of molecules, but life as we understand it operates on certain principles. For example, it uses complex molecules to create and control certain chemical reactions. We have enzymes made of protein that regulate chemical reactions so that the cell can produce energy from food, and use it to build new molecules, new DNA, to create new cells, or just engage in basic metabolism. And we believe that those general principles will apply to alien life as well. The big question for us really is, if we do find evidence of like, even just a simple cell, is it made from the same building blocks as us? Or is it made from a completely different set? we may be made of 22 amino acids, but there are thousands of possible amino acids that can occur spontaneously, which ones will have ended up being the building blocks of life, if they use the same building blocks as us that could imply that we come from a similar origin. So life on Mars could have come from earth or vice versa. And similarly, if they are made from a completely different set of building blocks, then that gives us a whole new insight into a different kind of biochemistry that we’ve never seen before. Whatever the answer is, it’s going to be fascinating, and will drive research for decades!

Chris
Oh my God, I am mind blown.

Alfredo Carpineti
I was at a conference in 2019, about how often there’s been contamination between Earth and Mars, because it’s perfectly possible for rocks from either planets after a big impact to fly to the other planet and land without getting too hot or be toodestroyed, so life could survive.

Joby
And I’ll just say that’s not a hypothetical. We have looked at Martian meteorites that we’ve found in Antarctica. So these are rocks that were knocked off Mars in an impact, hundreds of millions of years ago. We found intact amino acids in those. As far as we can tell, they just occurred through simple, like spontaneous, geochemistry. What we would call a biotic signatures rather than biological signatures. But we have found these basic building blocks in Martian meteorites. The big question is, can we find anything more complicated: like strings of amino amino acids, all hooked together into something that could potentially be a protein?

Alfredo Carpineti
That would be like… exciting!

Chris
So the amino acids that were found on these little pieces of rock in Antarctica, they are something that could imply building blocks of life, but they don’t necessarily imply actual life, they might be something else.

Joby
One issue we have, is even in Antarctica. That’s not a sterile environment. If those meteorites have been in Antarctica for any length of time, we cannot discount the possibility that they may be contaminated by terrestrial life post impact. So that’s the big question is we really need to detect these molecules in situ as in like it on the surface of Mars, to be absolutely sure that that’s where they came from.

Chris
Yep, that makes sense.

Alfredo Carpineti
Right? I think we answered the question “is there life of Mars?” the only way we can: by say that we have no clue!

Chris
It’s a solid maybe!

Alfredo Carpineti
t’s a solid maybe and we’re trying our best. Well, we’re not trying but people like Joby are trying their very best to find it.

Joby
I do enjoy the fact that I can legitimately talk about extraterrestrial life. I actually have used the phrase extraterrestrial life question mark in a paper that I have published. I really enjoy that.

Alfredo Carpineti
That is quite an accomplishment!

Chris
So exciting. This has been like, such an amazing episode. learn so much. And quite a lot of the answers have blown my mind.

Alfredo Carpineti
Likewise!

Joby
Yeah, we may not have a conclusive answer to the question of whether there is life on Mars. But even the information we’ve already found out has taught us so much about where we may have come from. And the possibilities of basically just trying to think about what could have happened on another world. Really extends the horizons of what we understand. So I like to think that there is no bad answer to the question of “is there life on Mars?” Because whatever we discover, we’re learning something really profound and really important that helps us find our own position in the universe.

Chris
What a note to end on.

Alfredo Carpineti
Couldn’t have said it better myself.

Chris
Thank you so much for being our special guest today.

Chris
Yes, thank you, Joby!

Joby
Oh, it’s been great. Thank you very much!