Although smaller than the Earth, Mars has been found to be a geologically very diverse place, often similar to our own planet but also sometimes quite different – a world that is both eerily familiar and uniquely alien.
Now, another new discovery has raised more questions about the planet’s past, and how similar geological processes have shaped the landscapes of both worlds.
Photographs taken by the Mars Reconnaissance Orbiter spacecraft of the Athabasca Valles region near the equator have revealed hundreds of odd spiral shapes on the surface. So far, 269 have been found, ranging up to about 30 metres (100 feet) across each, at Cerberus Palus specifically, an area where “plates” of material have fractured, rotated and drifted over time. On Earth, similar looking coils can be formed by “ice rafts” or slow-moving lava flows, either of which may also explain the platy, fractured appearance of the ground.
So how did these coils form? By fire or ice?
When pahoehoe lava flows on Earth slide past each other, moving at different speeds or in different directions, they can form twisted, coiled shapes similar to those seen on Mars.
According to Andrew Ryan, one of the authors of the new study published in the journal Science, ”Everything that we have observed in Athabasca Valles can be formed by lava. Although you could attribute certain features to ice, the lava coils indicate that this is not the case. There are no known mechanisms to naturally produce spiral patterns in ice-rich environments on the scale and frequency observed in our study area.”
But not all scientists are convinced about the lava explanation. They contend that water ice could still account for the curious spirals – as explained by John Murray of the Department of Earth Sciences at the Open University in the UK:
“I think there are so many features here that it’s difficult to explain them other than [the theory] that this was essentially water that froze and has since sublimated away. Sublimation is when a solid turns directly into a gas. There is no lava that behaves in so many different ways.”
He adds, ”You do get plates in lava, but on the scale of a few metres. Here you’re talking about things which are kilometres long, and the only way you can do that really is to have a liquid that’s extremely mobile and fluid – water or something like water. If you freeze the top of that, as in the Arctic, you do get ice floes that are several kilometres or more, which is what you get on Mars in this region. You never see anything like that in a lava flow.”
As with other Martian mysteries, the debate will probably continue for the forseeable future.
The paper is available here.
This article was first published on Examiner.com.