by Matthew Cobb
The BBC, together with Science Channel, has just produced an excellent five-part series, The Wonders of the Solar System, fronted by my colleague from the University of Manchester, physicist Professor Brian Cox (no, I haven’t met him). Cox is an extremely pleasant presenter who gets a lot of press because he is young (ish – 42), good looking (well, he has a lot of nice hair) and he used to be a pop star (he played keyboards in a band called D:Ream which had a 1994 hit with “Things can only get better”, which was notoriously played at the early morning celebration of the New Labour electoral victory in 1997).
His popularity is justified and undeniable – only three hours ago, one of my ex-students posted on Facebook “loves bryan cox. pop star and a physicist. amazing.” You can find an amusing profile of Cox here.
The series has used some fantastic astronomical images to show how studies of terrestrial geological phenomena can inform us about what’s happening on other planets in the solar system. The last episode in the series, which I have just watched, was on the possibility of extraterrestrial life. [There’s a BBC page about this episode here.] Cox’s focus being the solar system, he didn’t even mention the Fermi paradox (summed up in his question “where are they?” – given the size and age of the universe, the place should be heaving with bug-eyed monsters in flying saucers, but it clearly isn’t). Rather, he was interested in where there might be life in the solar system.
There are two current candidates, apart from our Goldilocks planet (not too hot, not too cold, just right) – the planet Mars and Europa, Jupiter’s moon. There’s a lot of speculation involved, but it’s still fascinating stuff. Europa is covered with ice, but it is continually fractured and shifting, and measurements indicate that there is a massive ocean of salt water underneath the surface – an ocean that may be 100km deep. This is an awful lot of liquid water (more than twice the amount on Earth), and Cox made the case that because we can find bacteria living and reproducing within ice on Earth, it may also be the case that similar organisms live in Europa’s ice-shell.
One problem, however, is that the very size of the ocean may exclude Europa as a source for genuinely alien life, for the simple reason that for life to evolve, it would require a very stable, static, tightly controlled environment for those fragile molecules to come together. And that will be absent in the swirling black depths of Europa’s ocean.
My feeling is that on Earth the evolution of the first self-replicating molecules – probably RNA – did not take place in “some warm little pond” as Darwin put it, but rather in some tiny bubbles in the mud on the edges of such a warm pond, that would be stable and secure enough, for long enough (perhaps hundreds of years or even more). In other words, something like a cell was required before those amazing reactions that produce life could evolve. In Europa’s case, my guess would be that something similar would be necessary (perhaps tiny bubbles in the ice) for replicant molecules to evolve.
The last time I suggested to Jerry that something like a cell (non-organic, of course) came before its contents, he was rather rude, but what does he know? Or me? Or anyone? It is the case that spherical “protobionts” made out fats occur spontaneously, “reproduce” and have semi-permeable membranes that can see various metabolic processes occur, as shown in this first-level undergraduate textbook:
Even more intriguing for me was the section that dealt with something I knew nothing about, and about which other views have tweeted their disbelief about: snottites. These are slimy structures found in some caves, which are formed by archea – simple bacteria – that are able to metabolise hydrogen sulphide (in a dramatic scene, Cox went deep into one of these caves, where the atmosphere was virtually unbreathable, his personal hydrogen sulphide alarm bleeping away), and they excrete sulphuric acid. When these organisms live in limestone caves, they actually help etch away the caves through their respiration.
The fact that I didn’t know about snottites is merely my ignorance (and shame). You can find a great NASA page about them here.
These are not only great extremophile organisms – they look like snot! they crap out acid! – it also reinforces the idea that even if all the conditions currently found on Earth are not met, life may still evolve. Including on Mars and Europa.
This is hardly surprising in a way – when life evolved here 3.5 billion years ago, Earth wasn’t like it is now. In particular, atmospheric oxygen levels were at about 0.0007% of what they are now. It took life itself to change that, in two vitally important events – the Great Oxidation Event (2.5 billion years ago which saw levels shoot up to around 8% of current, followed by another massive surge, up to present-day levels, around 650 million years ago, “shortly” before the Cambrian Explosion. But that’s another story.
Here’s a trailer for the ET episode of The Wonders of the Solar System (may not work outside UK…)
There’s also a great spoof of both Cox and the mind-bending amazingness of the solar system here. The success of the spoof owes much to the imitator getting Cox’s Oldham accent more or less spot on, and folk memories of the drug-crazed ramblings of Madchester bands like the Happy Mondays and the Stone Roses. Warning: contains rude words.