Is There Life on Mars? - Script (Patreon)

Probably not…

Maybe? I don't know.

There is no greater hero in our search for life on mars than a little robot named Opportunity. 15 years after its mission begin - 57 times longer than it signed up for - Opportunity has gone silent. As we wait and hope while NASA races to reestablish contact, we thought we'd reflect on the greater quest that Opportunity has contributed so much to. The search for life on Mars.

Mars. The red planet. Fourth rock from the Sun. It’s currently just past its closest approach to Earth, making it an angry red eye in the early night sky. This is a planet that, as far as we know, is inhabited entirely by robots. 

But at the end of July, something remarkable was announced that may prove the possibility of life on Mars. There’s a giant underground lake of liquid water on Mars. Right now. Under the south pole. And in 2020  the race to find life on Mars will intensify, with both the ESA and NASA launching missions. They’ll shift the focus from the search for water to the search for life, past or present. NASA’s also planning a mission to take a sample of Martian soil and rocket it back to Earth. Plying our best Earth-bound technologies to and uncontaminated sample may provide the proof of Marian Life we’ve always been hoping for. 

But as good scientists, we have to suggest some caution because people have searching for Life on Mars and believing they've found it,  for over three hundred years. And today we’re going to look back at the long history of life on Mars - or at least our hunt for it.

We begin our story at the end of the 17th century, when Dutch polymath Christiaan Huygens made amazing advances on Galileo’s astronomical telescope, allowing him to observe a dark patch on the Martian surface, and so measure Mars’ 24 hour rotation rate, as well as a white spot on its south pole. He guessed that these both resulted from surface water, clouds and ice. 

Huygens saw this as evidence that Mars was habitable, and so perhaps inhabited. In fact he was the first to postulate that liquid water is necessary for life. A few centuries of extra science has only convinced us more of that, as we’ve discussed before. Huygens was visionary in many ways, but only half right in his interpretation of his observations of Mars. The white spot was indeed a polar ice cap, but the dark spot was probably the volcanic rock of the Syrtis Major Planum. Nonetheless, the prospect of a watery Mars kicked off centuries of optimism for an inhabited planetary neighborhood.

Astronomer Giacomo Maraldi quickly followed Huygens, and in the early 18th century discovered ice caps on both poles, correctly inferring their nature. Later that century William Herschel watched the ice caps grow and shrink annually and thought he saw what he calls a comfortable but modest atmosphere. Herschel generously decreed of Mars that “it’s inhabitants probably enjoy a situation in many respects similar to ours”. Now Herschell was a fantastic astronomer, but his wrongness about Mars’s atmosphere is a nice example that even the smartest of us we see what we want to see. As a scientist, it’s so important to stay aware of that very human bias. Because it has lead to the erroneous discovery of life on Mars. On multiple occasions. 

Fast forward to 1877. Giovanni Schiaparelli was studying Mars during its perihelion opposition. That's the configuration that also just passed recently - Mars was at its closest to the Sun and the Earth at its closest to Mars. He observed streaks on the surface of the planet that he named "canali". That’s Italian for channels, presumably implying naturally formed flows of water. Perhaps in part with the newly made Suez Canal still fresh on people’s minds, canali was mistranslated in English to canals, implying artificially made structures. People see what they want to see and hear what they want to hear.

The prospect of a technological civilization on Mars inspired businessman turned astronomer Percival Lowell. He built himself an observatory and dedicate his career to studying Mars. The Lowell observatory is famous for the discovery of Pluto, but that was later. Lowell was obsessed with the Martian canals. He spent fifteen years making sophisticated drawings of its surface. Then he went full Ancient Aliens: Martian Edition. He believed that the canals were a relic of an ancient, advanced, civilization that built them to move water from the polar ice caps as a last ditch source of water on a drying planet. Lowell wrote three books on the subject, the last presenting his full theory on the subject of life on Mars. This popularized the belief in the general public of life on Mars, ultimately inspiring works of fiction like HG Wells’s The War of the Worlds or Ray Bradbury’s The Martian Chronicles. 

It turns out Lowell’s canals were just as fictional: probably a combination of artifacts from imperfect telescope optics plus actual erosion features. We had to actually go to Mars to really confirm this. In the 1960s and early 70s the Mariner missions conducted the first Mars fly-bys,  giving us our very first close ups of the planet. Mariner didn’t find canals, but it did find evidence of ancient river beds carved into the landscape. This evidence for ancient flowing water wasn’t definitive at the time. A closer look was needed. 

NASA landed Viking 1 and 2 on the surface of Mars in 1976. They conducted four experiments looking for the biosignatures of past or present microbial life. Three of the tests were negative, but the fourth was positive! It was the so-called labeled release experiment. In it, a soil sample is fed nurience laced with radioactive carbon 14. Any microbes should metabolize the nutrients and expel radioactive CO2. Right away, both probes detected these radioactive gasses.A general rule in science is that a result isn’t real until it’s repeatable. And this experiment failed that test a week later. While some thought that the initial Viking results were a positive active biosignature on Mars, most agree the results are inconclusive likely a result of some abiotic - non-living - reaction with the soil. And sadly not microscopic martians. 

And then there’s the famous martian fossil meteorite. This rock was discovered in Antarctica in 1984. Based on its chemical composition, it must have come from the Martian surface. Probably ejected from Mars’ gravitational field after another space rock smashed into the planet. It was dated to around 4 billion years old, from a time when we now believe liquid water was abundant on the surface of Mars. This rock held a tiny secret for all of those billions of years. And it would hold the secret for another decade still, until 1996 with the advent of higher resolution scanning electron microscopy and laser mass spectrometry. That analysis revealed chain structures that looked a lot like Earth microfossils. This “direct detection of extraterrestrial life” even prompted an announcement from President Clinton. But once again, it was probably a false alarm. Just like the Viking test results, these features could also be explained by non-biological processes. It’s never aliens … until there’s no other possible explanation.

All of these near misses did serve a powerful good - they inspired our continued obsession with the red planet, and so many more missions have followed. A series of orbiters, landers and rovers found increasing evidence of the past and present activity of water on Mars. The Mars Odyssey orbiter detected atmospheric hydrogen that told us of enormous quantities of water ice frozen into the Martian soil close to the poles. 

And that brings us to Opportunity. Otherwise affectionately known as Mars Exploration Rover B. It landed in 2004 with its twin - MER-A, better known as Spirit. These six-wheeled golf-cart-sized robots were swiss army knives of geological lab instruments. Opportunities most spectacular discovery where these cute little so-called berries. They turned out to be concretions of hematite - which means they were grown in wet environments with dissolved iron. Wet means water FYI. Both rovers found a variety of other geological signs of past water activity, really solidifying the picture of Mars' much more liquid past. Both rovers were supposed to shut down after around 90 days as Martian dust accumulated on their solar panels, cutting of their power supply. 

But unexpected "cleaning events" from the Martian wind cleared those accumulations, allowing both the massively exceed their expected lifespans.  Spirit did great, but eventually got bogged in a sand trap before shutting down. Opportunity just chugged on on and on. The vast Martian dust storm that has enveloped the planet since early June cause Opportunity to enter hibernation mode. As of the filming of this video, that storm is only starting to settle down. NASA - and all of us - remain hopeful that communication will be reestablished. If not, you've earned your rest, brave Opportunity.

The phoenix lander was the first to taste martian water, sampling the icy soil in the northern polar region. It found an abundance of perchlorate, a type of salt. That’s actually bad news. Perchlorates act as antifreeze, lowering the freezing point of water. This’ll be important later. Our latest Martian explorer - the curiosity rover - has sampled soil at lower latitudes and confirmed the presence of H2O in the soil planet-wide.

This brings us just about to the present. 2018 has been a great year for the possibility of life on mars. Two papers came out on the same June day. One reported the detection of methane in the atmosphere. So have we seen Martian microbe farts? Maybe, but not necessarily. Again, their are non-biotic processes that generate methane. The second paper was about organic matter found in mudstones on the Martian surface. Remember, “Organic” in chemistry just means a compound containing carbon. We find small organic molecules in lots of places that life has never touched. But the scientists think that these Martian molecules originated from large organic molecules called kerogens, which are often produced from the decay of once-living matter. And of course there are other, non-biotic ways to produce them. But all of these teases have got some scientists very excited.

But perhaps the coolest recent discovery is this  giant underground lake I mentioned at the beginning of the episode. At the end of July the European Space Agency announced that this lake was discovered using radar reflections from the MARSIS instrument on the Mars Express orbiter. This is the same way we map the ocean: by analyzing radio waves reflected from layers below the surface. And the MARSIS radar revealed a boundary between the surface ice cap and liquid water 1.5 km below, over a 20km wide area. 

It’s odd to find liquid water in a region that is surely several tens of degrees below freezing. But this is where those perchlorates come back. With enough of it, the freezing point of water could be as low as -75 celsius. So it’s an intensely cold, salty lake that even Earth’s most hardy extremophile organisms would have trouble with. But it’s a lake nonetheless. It’s a simple matter of drilling 1.5 km into the Martian ice cap to investigate it. Hey, here’s an idea: we should totally train some maverick deep-sea oil drillers to be astronauts and … Hmmm, no, that’s stupid. 

So, do I think there’s life on Mars? The planet was certainly wet and hospitable for long enough, and life didn’t take long to get started on Earth. It’s very plausible, and worth the hunt. After all, the payoff would be enormous. Finding even one incidence of life beginning on another planet would tell us worlds about the likelihood of life in the universe. Kind of a big deal if we want to understand our own place in what so far seems an eerily empty space time.