Friday Headlines, January 24, 2014
THE LATEST IN THE GEOSCIENCES
Magical mystery rock on Mars
We found land! …2.7 billion years ago.
It appeared unexpectedly. One day the Mars rover Opportunity snapped a photo of the ground next to it. About two weeks later, Opportunity took the photo again. The second photo was not like the first. A rock appeared, seemingly from nowhere. NASA scientists are baffled.
There are a few explanations for where the rock, now named Pinnacle Island rock, came from. Perhaps there was a meteor impact nearby, and the rock is merely ejecta. Or, maybe some invisible Martian life form put it there. The most plausible hypothesis is that one of Opportunity’s own wheels kicked it up and tossed it there.
Pinnacle Island rock is an unusual rock, unlike other rocks in the area. It’s high in sulfur, magnesium, and manganese, quite unlike anything else that’s ever been found on Mars before.
The best thing is that the Opportunity rover is what found it. The rover started its study of Mars on January 24, 2004 with a planned 90-day mission. Obviously, it’s far exceeded its expected lifetime and continues to help us discover amazing things about Mars.
About 70% of the modern surface of the Earth is covered with oceans. The remaining 30% is land that rises above the oceans. But there wasn’t always dry land. Nor were there always oceans, either.
We as geologists do know that continents have gradually gotten larger over geologic time. We also know that what forms the core of many continents was actually below sea level when it formed. So one might surmise that there may have been a time when there were oceans but no dry land.
When was that?
This new research shows that as long ago as 2.7 billion years ago – more than half of the Earth’s age of 4.6 billion years – that there were large land masses, exposed to erosion above sea level.
How do they know this?
Geochemistry. Geochemistry is always the answer. (OK, I’m just saying that because I’m a geochemist.) By examining the relative amounts of heavy elements like Hafnium and Neodymium, scientists were able to show that weathering of rocks, by forces like rain, snow, wind, and the Earth’s atmosphere itself, was occurring 2.7 billion years ago.
What the research doesn’t show, alas, is how big the land masses were, nor where they were exactly. At least we know now that continents did exist, and we’ve got more directions of research to go.