Was There Life On Mars Before Earth? | Unveiled

Was There Life on Mars Before Earth?

Around 3.5 billion years ago, the Earth was a very different place. Oxygen was extremely low, the ozone layer didn’t exist yet, and the planet’s surface was constantly blazed with radiation. Were a human being to be transported back there, they would die within a minute. But life still emerged. Tiny, unicellular microbes, forming the basis of everything to come. Today, we still have much to learn about our own planet’s early years… and yet there are some who say we should be looking elsewhere in the solar system if we want to truly understand.

This is Unveiled, and today we’re answering the extraordinary question; was there life on Mars before Earth?

Mars, like Earth, is roughly 4.5 billion years old. It formed, along with most of the rest of the solar system, out of an ancient, swirling cloud of dust and gas, at a time when the universe as a whole was about 9.3 billion years old. Mars is also a rocky planet, like Earth, and it’s the last of the inner planets closest to the sun before our particular star system is split in two by the Asteroid Belt. In some ways, Earth and Mars aren’t so different, but in others they’re poles apart.

Mars is around half of Earth’s size, it barely has an atmosphere to speak of, and it doesn’t have a magnetosphere. Crucially, it isn’t within most estimates for the habitable zone around our star, either. Not that this has stopped us looking for (and dreaming of) life on Mars in recent years. The archetypal alien from Mars has been a pop culture, science fiction mainstay for years, but actually science itself has moved on. Today, rather than scanning the Red Planet for an alien colony that’s alive and well, our rovers and orbiters are much more likely searching for signs of ancient life. From a time when Mars, perhaps, wasn’t quite so hostile. We may yet find a Martian environment hosting life today… but, if not, then evidence of life that once was is the next best thing.

The question of whether life on Mars, if it has ever existed, could’ve predated life on Earth was arguably first asked in earnest in 2013. Back then, NASA was busy analysing streams of data from its Opportunity and Curiosity rovers. Among many other things, the vehicles found solid evidence (whilst digging in rock) that Mars had once hosted large bodies of liquid water, and also that it is (and was) home to many of the most essential elements needed for life. This information has led to theories that microbes may have once existed on our neighbouring world, too, as they do on our own. Precisely when this period of possible habitability might’ve been is still up for debate, but many scientists and researchers place it somewhere between three and four billion years ago. Within the same, distant window, then, that the earliest life on Earth is thought to have spawned.

Before the rovers, though, there was Allan Hills 84001, a piece of Martian meteorite found in Antarctica in the last week of 1984. It’s thought that the rock, which weighs a little over four pounds, crashed into Earth some 13,000 years ago. The leading theory says that it was ejected from Mars following another impact event on the Red Planet, about 17 million years ago. But significantly, this meteorite can be dated back a little over four billion years in total. That’s long before even the upper estimates for unicellular life on Earth, which is interesting because Allan Hills 84001 also formed the basis of one of the first major news stories pertaining to evidence of life on Mars. Early study found what appeared to be tiny, microbial fossils in the rock. And while these observations were eventually rejected by most astrobiologists, the hubbub was enough for former US president Bill Clinton to make a televised speech in the mid-1990s, when analysis from the meteorite was made public.

So, that’s now a seemingly dubious rock found in Antarctica and some arguably more compelling findings from rovers on the surface, both hinting at the potential for life on Mars up to four billion years ago. Possibly at a time before even life on Earth arose. And there have been other studies pointing to similar conclusions, too. But, of course, it’s imperative to keep in mind that so far, we still have no solid proof of life on Mars at any time. We only have basis for various theories. But what would the planet have been like, so far back in history?

As much as Earth was a very different place billions of years ago, so too, it seems, was Mars. When we think of it today, we see stark, barren landscapes layered with dust and stripped of atmosphere. A merciless world without air to breathe, soil to grow, and with precious little hope for survival. But just as we now suspect there to have once been lakes and pools dotted across the Martian surface, we also believe that it did once host an atmosphere. And that it wasn’t always so bare.

Scientists estimate that up to sixty-six percent of the Martian atmosphere has been lost since its height around four billion years ago. One co-authored study, appearing in the journal “Science” in 2017, for example, outlined how the planet underwent a “transition in climate from an early, warm, wet environment to today’s cold, dry atmosphere”. That study made use of the Mars orbiter, MAVEN, to measure upper atmosphere levels of Argon, in particular. But those behind it say that the findings can also be applied to carbon dioxide levels, and therefore the presence of greenhouse gasses on Mars, as well as oxygen. At one time, these gasses may have been far more abundant on Mars… again leading to speculation that life, and especially microbial life, could’ve once thrived there.

Even today, Mars is still losing its atmosphere to space, with more and more particles escaping with every passing minute. But it’s thought that the majority of the loss did take place around four billion years ago. And as for the relatively short time between then and when the planet formed, we’re currently not overly confident as to what conditions were like. Naturally, though, it’s this unknown period which most fuels the majority of life-on-ancient-Mars theories. So, let’s imagine for the last part of today’s video, that life did once exist there… what could that mean for us?

In August 2020, a familiar, astrobiological theme made headlines once again: panspermia. Panspermia is the proposed passing of biological material from one planet to another, in a number of ways - the most often cited being by spacecraft or asteroids. The 2020 story centred on a study conducted by Tokyo University and JAXA, the Japan Aerospace Exploration Agency, in which scientists put dried bacteria into exposure panels on the outside of the International Space Station. Three years after doing so, they checked to see whether any of the bacteria had survived - and, incredibly, most of it had. The bacteria on the outermost layer did perish… but underneath it was still alive and well. We know, then, that in at least this one case, microbes could survive in space long enough to make a journey between Mars and Earth.

Lithopanspermia is, more specifically, the preservation of cells and microbes in rock, such as inside an asteroid. And we do have various examples throughout our history of Martian rock breaking away from its parent planet and ending up embedded in our own, including Allan Hills 84001. And so, herein lies the next question… If we ever proved that there was life on Mars before Earth, then could that life have been transported here? If you were to trace us back far enough, could we be the product of one-time Martian biology?

Importantly, again, panspermia is not a proven process. And, a lot of the time, space agencies are actually more concerned with how we could be the ones facilitating it the other way, by contaminating other planets with bacteria carried by our probes and rovers sent across the solar system. But it does prompt us to consider space in a wholly different manner. To see it as, potentially, a vast ecosystem of its own. Where life isn’t only confined to Earth, it just so happens to be here in abundance right now.

Mars has certainly changed over time. We know this thanks to an increasing number of studies. But could everything about us really have started out on a different planet? Fortunately, our interest in Mars is far from slowing down. In fact, it’s gathering pace as we move through the twenty-first century. Which means that if there ever was life there… then the signs will become clearer and clearer.

For now, the outlook’s still hazy, but the fog is lifting. And that’s why science can’t yet rule out that there was life on Mars before Earth.