It has been theorised for a long time that the dwarf planet Ceres may be harbouring a lot of water. With the promise of water comes the hope that life may be present on this little world orbiting the Sun in the asteroid belt. You may be forgiven in thinking that the search for life in the Solar System has gone a little crazy, after all, we haven’t found life anywhere else apart from our own planet. However, if we do discover life on other planetary bodies apart from Earth, perhaps the panspermia hypothesis is more than just an academic curiosity. So why is Ceres suddenly so interesting? Firstly, it probably has water. Secondly, the ex-asteroid is so small that fragments of Ceres could have been kicked into space by meteorite impacts more readily than other larger planetary bodies, making it a prime candidate for seeding life on Earth…
There’s always good news to outweigh the bad. In 2006 when the International Astronomical Union (IAU) demoted Pluto from being a “planet” to a “dwarf planet”, Ceres had the reversal in fortune in that it was promoted from being just another big asteroid to a dwarf planet. Now this tiny world has become a little more important.
In 2007, NASA launched the Dawn spacecraft that will reach this mysterious dwarf planet in 2015. It will be the first mission to this region of the Solar System, and it is making good progress (Dawn just completed a gravitational flyby of Mars). So far, since its discovery in 1801 by Giuseppe Piazzi, we have only managed to attain some fuzzy images of Ceres using the Hubble Space Telescope (pictured top). As can be seen from the size comparison, trying to spot Ceres is quite a task, it is tiny (in fact, it is the smallest classified dwarf planet out there, so far). This may be the case, but it is its low mass that has excited a University of Giessen (Germany) researcher who is studying the possibility that Ceres could support life.
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Although it is unknown whether or not Ceres has liquid water oceans, Joop Houtkooper believes that if it does, basic life forms may be thriving around hydrothermal vents in the hypothetical Ceres oceans. However, it is not clear how these proposed oceans can stay in a liquid state, as it seems unlikely there is significant tectonic activity (as it has very little mass to sustain a long-term molten core) and it is not orbiting a tidally disruptive body (like the icy moon Europa around Jupiter – extreme tidal forces maintain sub-surface oceans in a warm state). However, the idea remains as Ceres has a lower escape velocity than any other planetary body, meaning that microbes (hitch-hiking on fragments of Ceres) could have been kicked into space with more regularity than other planets, such as Mars.
“I looked at the different solar system bodies which either had or currently have oceans,” Houtkooper explains. “The planet Venus probably had an ocean early in its history, but the planet’s greater mass means that more force is needed to chip off a piece of the planetary crust and propel it in the direction of the Earth. Smaller objects like Ceres have lower escape velocities, making it easier for parts of it to be separated.”
Also, Ceres appears to have gotten off fairly lightly during the Late Heavy Bombardment, allowing it to retain its surface water. If the Earth had any life before this era, it is possible that the violent impacts sterilized the planet. In this case, it is possible life arrived to Earth via a shard of another planetary body in the form of a meteorite.
Although calculations suggest Ceres could be a very likely candidate as the source of panspermia, eventually leading to life on Earth, the question as to whether Ceres is even a hospitable place for life to form is doubtful. Also, if Ceres was saved from the worst impacts during the Late Heavy Bombardment, and it appears to have retained the majority of its water through lack of impacts, surely Ceres fragments would be a very rare meteorite component?
Still, it is an engrossing area of research, but we’ll have to wait until Dawn arrives in Ceres orbit in a little over five years time before we arrive at any answers…