One of the age-old questions for which an answer has long eluded humankind is the story of our origin. Current scientific knowledge has enabled us to trace our evolutionary history back through the earth’s past, thanks to fossil records from different eras. It is now widely accepted that life on earth likely started from ocean-based lifeforms, until some of these slowly evolved feet and moved onto dry land, eventually giving rise to all land-based life we see today.

Going even further back in time, the first lifeforms on earth were likely single-celled organisms in earth’s ancient oceans, which ultimately started clumping together to form more complex organisms. Yet, the question as to where these very first known lifeforms themselves came from remains very much unanswered.

A related question to this is – are we alone in the universe? Is the fact that we have never seen life beyond our planet a result of our inadequate, weak instruments? Is it perhaps because of the vast distances in the cosmos making communication between lifeforms on different planets in different solar systems too difficult? Or is it perhaps because life is indeed too rare, perhaps unique to earth?

Countless studies have tried to answer these very questions, to understand if conditions like those known to have been present on earth around three billion years ago, when the first lifeforms suddenly appear in our fossil records, exist elsewhere. What we found is, they definitely do. We didn’t have to look very far either.

Saturn’s moon, Titan, is perhaps the most unique body in the solar system, apart from our own planet. The only moon known to have a substantial atmosphere in the solar system, its atmosphere is even more voluminous than earth’s. A thick haze layer, composed of complex hydrocarbons, shrouds the moon’s surface from view. However, thanks to the Cassini spacecraft and the Huygens probe, the latter of which landed on the moon in January 2005, we now know that Titan has a landscape very similar to earth’s. The processes that shape the valleys and plains on Titan are due to liquid methane, which acts on the moon like liquid water here on earth. Its atmosphere is largely (95 per cent) made up of nitrogen, with methane making up most of the rest of the atmospheric constitution.

What makes Titan of particular significance is that this atmospheric composition is very similar to that believed to have been present on earth about three billion years ago. Had it not been for Titan’s freezing temperatures due to its location in the outer reaches of our solar system, the same conditions that were present on Earth when the first lifeforms appeared on our planet could be present there as well, rendering Titan akin to a frozen relic of Earth’s distant pre-biotic past.

In my undergraduate studies, I simulated the conditions currently present on this moon and how these are expected to change over the course of the next few billion years. During this time frame, the sun will evolve into a red giant, increasing the amount of solar energy which Titan receives. This will occur in five billion years’ time, at which point the earth would have long become uninhabitable due to the soaring temperatures as a result of the expanding sun.

The first results from my studies showed that Titan will experience an increase in temperature, while keeping a similar atmospheric composition, and so could indeed host conditions even more similar to those present on pre-biotic earth three billion years ago.

If any processes giving rise to life occurred on earth back then as a result of those specific conditions, they might occur again on Titan in a few billion years.

Josef Borg is currently a PhD student within the Institute of Space Sciences and Astronomy, University of Malta, and also vice-president of the Astronomical Society of Malta.

Did you know?

• Saturn’s rings are likely the result of a moon which wandered too close to the gas giant. Famed for its iconic rings, Saturn probably didn’t always have its rings, and nor will they remain forever. It is hypothesised that in their place, there was once a moon not unlike the several other moons still orbiting Saturn to this day, of which Titan is by far the largest. This moon wandered too close to Saturn, and the resulting gravitational tug of the giant planet resulted in it breaking apart, leaving behind a ring of small pieces of ice and rocks. Eventually, the rings are expected to draw in closer and closer to Saturn until they are drawn into the planet itself, over millions of years.

• Titan has a methane cycle, with methane lakes and methane precipitation. Although it might be a bit hard to imagine, Titan has lakes, similar in appearance to those on earth, except for the fact that surface temperature on Titan is so cold that liquid water could never exist at the surface. Instead, these lakes are mostly methane, with some other simple hydrocarbons also present. Methane evaporates, forms clouds and then precipitates to the surface, analogous to what we see on earth with water. Erosion processes from methane flows on the surface, both in the past and currently, have shaped the moon’s topography.

• Life on earth will be impossible in around one billion years. Although the sun will not expand to a red giant for another five billion years, it will steadily increase its energy output in the time between now and then. As it does so, temperatures on earth will also steadily increase and eventually soar beyond the boiling point of water, rendering our planet sterile. This bleak future for our planet is inevitable, and yet it may mean that other worlds further out in our solar system might eventually host conditions more hospitable for life themselves.

For more trivia see: www.um.edu.mt/think

Sound bites

• Amateur astronomer captures supernova’s first light. Observing the exact moment that a supernova explodes has long been a challenge for astronomers. Initiatives are under way to catch this fleeting moment, but it’s an amateur astronomer who now claims the earliest detection of a supernova. Once the supernova was confirmed, receiving the official designation SN 2016gkg, extensive monitoring began, including with the Neil Gehrels Swift Observatory, which took X-ray, ultraviolet, and visible-light observations. However, amateur astronomer Buso had captured the most valuable information in the earliest hours of the stellar explosion.

http://www.skyandtelescope.com/astronomy-news/amateur-astronomer-captures-supernovas-first-light/

• Astronomers watch donut rotate around supermassive black hole. Astronomers have detected a torus rotating around the supermassive black hole at the centre of spiral galaxy Messier 77, collecting observations that may shed light on why these weird structures exist. Such a structure ought to collapse into a disk within 100,000 years. Instead, they apparently stick around for hundreds of millions of years, and astronomers still don’t know why.

http://www.skyandtelescope.com/astronomy-news/astronomers-watch-donut-rotate-around-supermassive-black-hole/

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