Science

13 October 2024: Ringing in the changes
Missing something? Perhaps. Earth may once have had rings. Photo: NASA, The Blue Marble.

When I was a wee lad with a growing interest in astronomy and science fiction, I sometimes wondered what it would have been like if Earth, like Saturn, had a ring.

As it turns out, not great, apparently.

In a paper published in Science Direct, Andrew Tomkins, Erin Martin and Peter Cawood suggest Earth may indeed have had a ring during the Ordovician, around 466 million years ago (Ma) with intriguing but catastrophic consequences.

As Tomkins explains in an article for The Conversation, the first clue for the team was an anomalous series of 21 impact craters from around that time, combined with ‘deposits of limestone across Europe, Russia and China containing very high levels of debris from a certain type of meteorite.’

The team then mapped where the craters would have been 466 Ma by using models of tectonic plate movement. Turns out they were all along the equator, with none near the poles.

As Tomkins writes, ‘… we measured how much of Earth’s land surface suitable for preserving a crater was near the equator at that time. Only about 30% of the suitable land was close to the equator, with 70% at higher latitudes.’

So, odds on something peculiar was going on.

The team speculates that Earth captured a passing asteroid which got close enough to exceed the Roche limit (where a smaller body’s internal gravity is overwhelmed by the tidal forces of a larger body). The broken remains of this asteroid then formed a ring around the Earth’s equator, and over time bits of it crashed into the Earth’s surface, forming the impact craters.

Finally, Tomkins et al speculated that the ring would have cast a shadow across large swathes of the Earth’s surface, which together with atmospheric dust from the impacts may explain the sudden plunge into what’s called the Hirnantian Ice Age about 445 Ma.

The team then further speculates that this rapid cooling would have forced animals to adapt to changing conditions, leading to the Great Ordovician Biodiversification Event. Uncomfortably abbreviated to GOBE, this was when Palaeozoic fauna replaced Cambrian fauna, leading to ‘… a spectacular increase in marine biodiversity at all taxonomic levels … ‘[i]

So  wearing a ring was not all bad news, I suppose.

[i] Servais, Thomas, et al ‘The Great Ordovician Biodiversification Event (GOBE): The palaeoecological dimension’, ScienceDirect. See here.

31 March 2021: Photosynthesis without sunlight

An organism has been found that photosynthesises from light coming from hydrothermal vents 2400 metres below the sea. It is the first photosynthetic organism discovered that does not rely on sunlight.

As reported in a paper pithily titled ‘An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent’ published in the journal of the Proceedings of the National Academy of Sciences, the green sulphur bacteria was found living near a thermal vent off the coast of Mexico called 9 North.

One of the paper’s authors is Professor Robert Blankenship from Arizona State University’s chemistry and biochemistry department. In an interview with Skip Derra (posted on the university’s website) , Blankenship said the bacteria uses a chlorosome complex which acts like a satellite dish to collect any light it can and transfer it to the organism’s reaction centre where the photosynthesis takes place.

Blankenship also said the discovery was important not just for what it meant for life on earth, but what it means for the search for life outside of Earth.

‘This shows that photosynthesis is something that is not limited only to the very surface of our planet,’ he says. ‘It lets you consider other places where you might find photosynthesis on Earth, as well as on other planets.’

As the original paper’s abstract reflects:

‘The abundance of life on Earth is almost entirely due to biological photosynthesis, which depends on light energy. The source of light in natural habitats has heretofore been thought to be the sun, thus restricting photosynthesis to solar photic environments on the surface of the Earth. If photosynthesis could take place in geothermally illuminated environments, it would increase the diversity of photosynthetic habitats both on Earth and on other worlds that have been proposed to possibly harbor life.’

Something for us science fiction writers to ponder.

Another amazing aspect of this paper is its relative obscurity: the paper was published in June 2005. If not for the heads-up in a recent post by Jerry Coyne on his website Why evolution is true, I doubt I would ever have learned about it.