Is There Life on Mars?

Is There Life on Mars?


Perhaps the most important question we can possible ask is, “are we alone in the Universe?”.

And so far, the answer has been, “I don’t know”. I mean, it’s a huge Universe, with hundreds of billions of stars in the Milky Way, and now we learn there are trillions of galaxies in the Universe.

Is there life closer to home? What about in the Solar System? There are a few existing places we could look for life close to home. Really any place in the Solar System where there’s liquid water. Wherever we find water on Earth, we find life, so it make sense to search for places with liquid water in the Solar System.

I know, I know, life could take all kinds of wonderful forms. Enlightened beings of pure energy, living among us right now. Or maybe space whales on Titan that swim through lakes of ammonia. Beep boop silicon robot lifeforms that calculate the wasted potential of our lives.

Sure, we could search for those things, and we will. Later. We haven’t even got this basic problem done yet. Earth water life? Check! Other water life? No idea.

It turns out, water’s everywhere in the Solar System. In comets and asteroids, on the icy moons of Jupiter and Saturn, especially Europa or Enceladus. Or you could look for life on Mars.

Sloping buttes and layered outcrops within the "Murray formation" layer of lower Mount Sharp. Credit: NASA
Sloping buttes and layered outcrops within the “Murray formation” layer of lower Mount Sharp. Credit: NASA

Mars is similar to Earth in many ways, however, it’s smaller, has less gravity, a thinner atmosphere. And unfortunately, it’s bone dry. There are vast polar caps of water ice, but they’re frozen solid. There appears to be briny liquid water underneath the surface, and it occasionally spurts out onto the surface. Because it’s close and relatively easy to explore, it’s been the place scientists have gone looking for past or current life.

Researchers tried to answer the question with NASA’s twin Viking Landers, which touched down in 1976. The landers were both equipped with three biology experiments. The researchers weren’t kidding around, they were going to nail this question: is there life on Mars?

In the first experiment, they took soil samples from Mars, mixed in a liquid solution with organic and inorganic compounds, and then measured what chemicals were released. In a second experiment, they put Earth organic compounds into Martian soil, and saw carbon dioxide released. In the third experiment, they heated Martian soil and saw organic material come out of the soil.

The landing site of Viking 1 on Mars in 1977, with trenches dug in the soil for the biology experiments. Credit: NASA/JPL
The landing site of Viking 1 on Mars in 1977, with trenches dug in the soil for the biology experiments. Credit: NASA/JPL

Three experiments, and stuff happened in all three. Stuff! Pretty exciting, right? Unfortunately, there were equally plausible non-biological explanations for each of the results. The astrobiology community wasn’t convinced, and they still fight in brutal cage matches to this day. It was ambitious, but inconclusive. The worst kind of conclusive.

Researchers found more inconclusive evidence in 1994. Ugh, there’s that word again. They were studying a meteorite that fell in Antarctica, but came from Mars, based on gas samples taken from inside the rock.

They thought they found evidence of fossilized bacterial life inside the meteorite. But again, there were too many explanations for how the life could have gotten in there from here on Earth. Life found a way… to burrow into a rock from Mars.

NASA learned a powerful lesson from this experience. If they were going to prove life on Mars, they had to go about it carefully and conclusively, building up evidence that had no controversy.

Greetings from Mars! I’m Spirit and I was the first of two twin robots to land on Mars. Unlike my twin, Opportunity, I’m known as the hill-climbing robot. Artist Concept, Mars Exploration Rovers. NASA/JPL-Caltech
Artist Concept, Mars Exploration Rovers. NASA/JPL-Caltech

The Spirit and Opportunity Rovers were an example of building up this case cautiously. They were sent to Mars in 2004 to find evidence of water. Not water today, but water in the ancient past. Old water Over the course of several years of exploration, both rovers turned up multiple lines of evidence there was water on the surface of Mars in the ancient past.

They found concretions, tiny pebbles containing iron-rich hematite that forms on Earth in water. They found the mineral gypsum; again, something that’s deposited by water on Earth.

Opportunity's Approach to 'Homestake'. This view from the front hazard-avoidance camera on NASA's Mars Exploration Rover Opportunity shows the rover's arm's shadow falling near a bright mineral vein informally named Homestake. The vein is about the width of a thumb and about 18 inches (45 centimeters) long. Opportunity examined it in November 2011 and found it to be rich in calcium and sulfur, possibly the calcium-sulfate mineral gypsum. Opportunity took this image on Sol 2763 on Mars (Nov. 7, 2011). Credit: NASA/JPL-Caltech
A bright mineral vein informally named Homestake. The vein is about the width of a thumb and about 18 inches (45 centimeters) long. Opportunity examined it in November 2011 (Sol 2763) and found it to be rich in calcium and sulfur, possibly the calcium-sulfate mineral gypsum. Credit: NASA/JPL-Caltech

NASA’s Curiosity Rover took this analysis to the next level, arriving in 2012 and searching for evidence that water was on Mars for vast periods of time; long enough for Martian life to evolve.

Once again, Curiosity found multiple lines of evidence that water acted on the surface of Mars. It found an ancient streambed near its landing site, and drilled into rock that showed the region was habitable for long periods of time.

In 2014, NASA turned the focus of its rovers from looking for evidence of water to searching for past evidence of life.

Curiosity found one of the most interesting targets: a strange strange rock formations while it was passing through an ancient riverbed on Mars. While it was examining the Gillespie Lake outcrop in Yellowknife Bay, it photographed sedimentary rock that looks very similar to deposits we see here on Earth. They’re caused by the fossilized mats of bacteria colonies that lived billions of years ago.

A bright and interestingly shaped tiny pebble shows up among the soil on a rock, called "Gillespie Lake," which was imaged by Curiosity's Mars Hand Lens Imager on Dec. 19, 2012, the 132nd sol, or Martian day of Curiosity's mission on Mars. Credit: NASA / JPL-Caltech / MSSS.
A bright and interestingly shaped tiny pebble shows up among the soil on a rock, called “Gillespie Lake,” which was imaged by Curiosity’s Mars Hand Lens Imager on Dec. 19, 2012, the 132nd sol, or Martian day of Curiosity’s mission on Mars. Credit: NASA / JPL-Caltech / MSSS.

Not life today, but life when Mars was warmer and wetter. Still, fossilized life on Mars is better than no life at all. But there might still be life on Mars, right now, today. The best evidence is not on its surface, but in its atmosphere. Several spacecraft have detected trace amounts of methane in the Martian atmosphere.

Methane is a chemical that breaks down quickly in sunlight. If you farted on Mars, the methane from your farts would dissipate in a few hundred years. If spacecraft have detected this methane in the atmosphere, that means there’s some source replenishing those sneaky squeakers. It could be volcanic activity, but it might also be life. There could be microbes hanging on, in the last few places with liquid water, producing methane as a byproduct.

The European ExoMars orbiter just arrived at Mars, and its main job is sniff the Martian atmosphere and get to the bottom of this question.

Are there trace elements mixed in with the methane that means its volcanic in origin? Or did life create it? And if there’s life, where is it located? ExoMars should help us target a location for future study.

The European/Russian ExoMars Trace Gas Orbiter (TGO) will launch in 2016 and sniff the Martian atmosphere for signs of methane which could originate for either biological or geological mechanisms. Credit: ESA
The European/Russian ExoMars Trace Gas Orbiter (TGO) will sniff the Martian atmosphere for signs of methane which could originate for either biological or geological mechanisms. Credit: ESA

NASA is following up Curiosity with a twin rover designed to search for life. The Mars 2020 Rover will be a mobile astrobiology laboratory, capable of scooping up material from the surface of Mars and digesting it, scientifically speaking. It’ll search for the chemicals and structures produced by past life on Mars. It’ll also collect samples for a future sample return mission.

Even if we do discover if there’s life on Mars, it’s entirely possible that we and Martian life are actually related by a common ancestor, that split off billions of years ago. In fact, some astrobiologists think that Mars is a better place for life to have gotten started.

Not the dry husk of a Red Planet that we know today, but a much wetter, warmer version that we now know existed billions of years ago. When the surface of Mars was warm enough for liquid water to form oceans, lakes and rivers. And we now know it was like this for millions of years.

A conception of an ancient and/or future Mars, flush with oceans, clouds and life. Credit: Kevin Gill.
A conception of an ancient Mars, flush with oceans, clouds and life. Credit: Kevin Gill.

While Earth was still reeling from an early impact by the massive planet that crashed into it, forming the Moon, life on Mars could have gotten started early.

But how could we actually be related? The idea of Panspermia says that life could travel naturally from world to world in the Solar System, purely through the asteroid strikes that were regularly pounding everything in the early days.

Imagine an asteroid smashing into a world like Mars. In the lower gravity of Mars, debris from the impact could be launched into an escape trajectory, free to travel through the Solar System.

We know that bacteria can survive almost indefinitely, freeze dried, and protected from radiation within chunks of space rock. So it’s possible they could make the journey from Mars to Earth, crossing the orbit of our planet.

Even more amazingly, the meteorites that enter the Earth’s atmosphere would protect some of the bacterial inhabitants inside. As the Earth’s atmosphere is thick enough to slow down the descent of the space rocks, the tiny bacterialnauts could survive the entire journey from Mars, through space, to Earth.

In February 2013, asteroid DA 2014 safely passed by the Earth. There are several proposals abounding about bringing asteroids closer to our planet to better examine their structure. Credit: NASA/JPL-Caltech
Credit: NASA/JPL-Caltech

If we do find life on Mars, how will we know it’s actually related to us? If Martian life has the similar DNA structure to Earth life, it’s probably related. In fact, we could probably trace the life back to determine the common ancestor, and even figure out when the tiny lifeforms make the journey.

If we do find life on Mars, which is related to us, that just means that life got around the Solar System. It doesn’t help us answer the bigger question about whether there’s life in the larger Universe. In fact, until we actually get a probe out to nearby stars, or receive signals from them, we might never know.

An even more amazing possibility is that it’s not related. That life on Mars arose completely independently. One clue that scientists will be looking for is the way the Martian life’s instructions are encoded. Here on Earth, all life follows “left-handed chirality” for the amino acid building blocks that make up DNA and RNA. But if right-handed amino acids are being used by Martian life, that would mean a completely independent origin of life.

Of course, if the life doesn’t use amino acids or DNA at all, then all bets are off. It’ll be truly alien, using a chemistry that we don’t understand at all.

There are many who believe that Mars isn’t the best place in the Solar System to search for life, that there are other places, like Europa or Enceladus, where there’s a vast amount of liquid water to be explored.

But Mars is close, it’s got a surface you can land on. We know there’s liquid water beneath the surface, and there was water there for a long time in the past. We’ve got the rovers, orbiters and landers on the planet and in the works to get to the bottom of this question. It’s an exciting time to be part of this search.

Curiosity Rover’s Proximity To Possible Water Raises Planetary Protection Concerns

After four years on Mars, the Curiosity rover has made some pretty impressive discoveries. These have ranged from characterizing what Mars’ atmosphere was like billions of years ago to discovering organic molecules and methane there today. But arguably the biggest discovery Curiosity has made has been uncovering evidence of warm, flowing water on Mars’ surface.

Unfortunately, now faced with what could be signs of water directly in its path, NASA is forced to enact strict protocols. These signs take the form of dark streaks that have been observed along the sloping terrain of Aeolis Mons (aka. Mount Sharp), which the rover has been preparing to climb. In order to prevent contamination, the rover must avoid any contact with them, which could mean a serious diversion.

These sorts of dark streaks are known as recurring slope lineae (RSLs) because of their tendency to appear, fade away and re­appear seasonally on steep slopes. The first RSLs were reported in 2011 by the Mars Reconnaissance Orbiter in a variety of locations, and are now seen as proof that water still periodically flows on Mars (albiet in the form of salt-water).

Mosaic of the Valles Marineris hemisphere of Mars, similar to what one would see from orbital distance of 2500 km. Credit: NASA/JPL-Caltech
Mosaic of the Valles Marineris hemisphere of Mars, as it would appear from orbit. Credit: NASA/JPL-Caltech

Since that time, a total of 452 possible RSLs have been observed, mostly in Mars’s southern mid-latitudes or near the equator (particularly in Mars’ Valles Marineris). They are generally a few meters wide, and appear to lengthen at the warmest times of the year, then fade during the colder times.

These seasonal flows of salt water are believed to have come from ice trapped about a meter below the surface. Ordinarily, such features would present an opportunity to conduct research. But doing so would cause the water source to be contaminated by Earth microbes aboard Curiosity. And right now, Curiosity has bigger fish to fry (so to speak).

During its planned climb, Curiosity was supposed to pass within a few kilometers of an RSL. However, if NASA determines that the risk is too high, the rover will have to alter its course. Unfortunately, that presents a major challenge, since there is currently only one clear route between Curiosity’s current location and its next destination.

But then again, Curiosity may not have to alter its course at all. Or it could find a route that lets it still accomplish its scientific goals, depending on the circumstances. As Ashwin R. Vasavada, the Project Scientist at the Mars Science Laboratory, told Universe Today via email:

“It may depend on the distance between the rover and a potentially sensitive region, for example.  Based on that understanding, we’ll determine the right course of action. For example, it may be possible to achieve Curiosity’s science goals while maintaining a safe distance. Another possible outcome is that we determine that there are no Recurring Slope Lineae on Mount Sharp.”

MRO image of Gale Crater illustrating the landing location and trek of the Rover Curiosity. In 2 years, Curiosity traversed 3 miles to reach the base of Mount Sharp. The next two years of trekking are likely to be at least as challenging. (Credits: NASA/JPL, illustration, T.Reyes)
MRO image of Gale Crater illustrating the landing location and trek of the Rover Curiosity. Credit: NASA/JPL, illustration, T.Reyes

For years, NASA scientists have been seeking to obtain samples from different locations around Mount Sharp. By studying the sedimentary deposits in the mountainside, the rover’s science team hopes to see how Mars’ environment changed over the past 3 billion years. As Vasavada explained:

“Curiosity’s science mission has focused on understanding whether the area around 5-km high Mount Sharp ever had conditions suitable for life. We’ve already found evidence for an ancient, 3-billion-year-old habitable environment out on the plains around the mountain, and in the lowest levels of the mountain.”

“The geology indicates that a series of lakes once was present in the basin of the crater, before the mountain took shape. Curiosity will continue climbing lower Mount Sharp to see how long these habitable conditions lasted. Every step higher we go, we encounter rocks that are a bit younger, but still around 3 billion years old.”

In the end, the job of determining the risk falls to NASA’s Planetary Protection Office. In addition to reviewing the current predicament, the issue of pre-mission safety standards is also likely to come up. Prior to its deployment to Mars, the Curiosity rover was only partially sterilized, and it is currently unknown how long Earth microbes could survive in the Martian atmosphere, or how far they could be carried in Mars’ atmosphere.

These dark streaks, called recurring slope lineae, are on a sloped wall on a crater on Mars. A new study says they may have been formed by boiling water. Image: NASA/JPL-Caltech/Univ. of Arizona
These dark streaks, called recurring slope lineae (RSL), are on the sloped wall of a crater on Mars. Credit: NASA/JPL-Caltech/Univ. of Arizona

Answering these questions and coming up with new protocols that will address them in advance will come in handy for future missions – particularly the Mars 2020 Rover mission. In the course of its mission, which will include obtaining samples and leaving them behind for possible retrieval by a future crewed mission, the rover is likely to encounter several RSLs.

One of the Mars 2020 rover’s primary tasks will be finding evidence of microbial life, so ensuring that Earth microbes don’t get in the way will be of extreme importance. And with crewed missions on the horizon, knowing how we can prevent contaminating Mars with our own germs (of which there are many) is paramount!

On its currently project path, the Curiosity rover would not get closer than 2 km from the potential RSL (which it is currently 5 km from). And as Vasavada indicated, it is not known at the present time what alternate routes Curiosity could take, or if a diversion in the rover’s path will effect it’s overall mission.

“It’s unclear at this time,” he said. “But I’m optimistic that we can find a solution that protects Mars, allows us to accomplish our mission goals, and even gives us new insight into modern water on Mars, if it is there.”

Further Reading: Nature