Are We the Martians Under the Bed?

Abiogenesis is the process by which life arises from non-living matter. Before reading my new favorite book, The Eerie Silence: Searching for Ourselves in the Universe by Paul Davies, I took it for granted that life must have emerged on Earth. Indeed, among the many theories discussed, this is still probably the most widely accepted view. However, as Davies explains, it is possible that our roots may actually lie on Mars.

1. Why Don't We Know?

One of the reasons why this question remains so difficult to answer is that Earth's oldest geological record has largely been lost. The Earth's surface has continuously been reshaped by plate tectonics, erosion, and weathering. The sedimentary rocks that preserve signs of life best are generally much younger, largely because photosynthesis has produced vast amounts of biomass at the Earth's surface over the last 2.5 billion years. Although there is an almost universal consensus that traces of life dating back 3.5 billion years exist in the Pilbara region of Western Australia, and even older potential traces have been found in Greenland—one of the oldest and best-preserved pieces of the Earth's crust, which once formed the seafloor of ancient oceans—the evidence for life's very beginnings has largely disappeared ¹²³. Because the Earth's earliest geological record is so poorly preserved, we lack empirical evidence for how life was created, and many ideas about abiogenesis are instead investigated through laboratory experiments ².

2. Why Mars?

During the first 700 million years of their history, both Earth and Mars were impacted by large boulders and asteroids, which would have hindered the formation, evolution, and preservation of life, particularly surface life ¹². Earth, however, experienced more of these impactors due to its stronger gravity; for example, the collision with Theia, the Mars-sized object from which part of the material would later form our Moon, may have sterilized our planet ⁴. Mars also cooled down faster due to being only about 10% as massive as Earth, resulting in potentially stable surface conditions earlier than on Earth.

Many of the hypotheses for the origin of life, including the popular marine hydrothermal vent and hot spring hypotheses, have also been proposed as possible, and in some cases even more favourable, environments on Mars that could have supported the emergence of life ⁵. For example, warm freshwater ponds, such as those found in volcanic regions or around hot springs, provide compelling conditions for the emergence of life. It is this latter environment that makes Mars particularly interesting. Ancient Martian hot springs would likely have been far more stationary than those on Earth because of the planet's much lower levels of tectonic activity ⁵.

Luckily for us, this, combined with Mars' much lower weathering rates throughout its history, has resulted in the planet preserving a far older and better geological record than Earth. Therefore, Mars could potentially be the place where we eventually discover the earliest traces of life.

3. From a galaxy far away?

This naturally begs the question: if life could have emerged on Mars and travelled to Earth aboard meteorites, could it not also have travelled to us from a galaxy far away? The broader idea that life originated elsewhere in the universe and spread between planets is known as panspermia.

Probably not from another galaxy. The gap between the Milky Way and the Andromeda Galaxy, our nearest large galactic neighbour, is about 2.5 million light-years. A rock would require billions of years to cross such a distance, and no known microbe or spore shielded inside a meteorite could survive exposure to cosmic radiation for that long. Of course, if life had been deliberately transported by an advanced civilisation, this would still remain a possibility, although one that is considered much more fringe.

Within our own Solar System, however, there are multiple worlds from which life could also have potentially travelled, albeit less plausibly than from Mars.

All in all, incredible as it already is that life emerged on Earth, I find it even more exciting to think that our oldest relatives may have lived somewhere we could not meet (yet) for Sunday brunch. Greetings to them from Earth!

Disclaimer: Things are not very accurate, but due to the fact that I've only just really read one book about it, and that this text will not be a scientific source, I will leave it at this. — Merel out.

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