I’ve been working on some more astrobiology art. It’s taken on a life of its own, and I have to say, I’m paying more attention to these images than my YouTube channel!
I’ve been enamoured lately of dead or dying worlds. A recent video on my channel talked about the amazing possibility of limestone fragments orbiting the white dwarf star SDSSJ1043+0855. Ever since reading of this it’s captured my imagination. The notion that life has existed long ago, possibly before life began on earth bears thinking about.
Limestone is a mineral produced primarily by organisms which produce shells, using a matrix that incorporates calcium carbonate. In the early days of multicellularity, as the predator-prey paradigm took hold of Darwinian evolution, an ancestor of today’s molluscs discovered how to make use of an upsurge in calcium levels in the oceans. It used it to produce a protective suit of armour. This trick was so successful that molluscs became incredibly abundant. So abundant, in fact, that their remains ended up as vast deposits of limestone.
To the present day.
Using spectroscopy, the three elements that comprise calcium carbonate: carbon, oxygen and calcium have been detected in the upper atmosphere of this particular white dwarf. By themselves they aren’t a smoking gun. It’s also fair to point out that limestone can form abiotically. Limestone deposits in subterranean caves are one example. However, the vast majority of limestone on earth is biologically produced.
The “limestone” orbiting this star is believed to be embedded in the fragments of a large rocky object. We know nothing about this world, only that it probably existed and (possibly) limestone comprised part of it. Is it a fossil, spotted across the light years by modern humans? How long ago did this world harbour life? White dwarf stars (which aren’t technically stars! Find out why here) have been discovered which are nearly as old as the universe.
Earth is 4.6 billion years old. What of the world currently being torn up by the immense gravity of this white dwarf?
It would be interesting to look forward and see how our own world eventually will die. For now, this white dwarf star and it’s companions are a way to look ahead at what may befall us. It’s believed that eventually the earth will become incapable of supporting life, as the sun begins to undergo senescence billions of years from now. What iterations will the terrestrial biosphere take over such a vast stretch of time? Will life start over? Are these “fossil” fragments within this unnamed rocky world pieces of its last ecosystems?
What will the last ecosystem on earth be?