Friday Headlines, February 28, 2014
THE LATEST IN THE GEOSCIENCES
Oldest mineral on Earth is 4.4 billion years old.
Is Yellowstone about to blow? (Answer: No.)
More evidence for life on Mars
This headline is particularly apropos, since those few weeks ago when the Nye-Ham debate took place. One of the things that Ham asserted was that nothing on Earth had been dated back to the beginning of the Earth (approximately 4.6 billion years ago). When he said that, I knew that to not be true, at least in the sense that we had most definitely dated things back into the billions of years ago.
And then this headline crossed my desk.
Here, a single zircon crystal was dated at 4.4 billion years ago. Well that’s pretty darn close to the beginning of the Earth. Hah!
You’re asking (yes, I can hear you), how would you find a single zircon to date? Where does this come from?
Zircons are hardy little crystals. They form in igneous rocks from the cooling of molten magma. Over hundreds of millions of years, the original igneous rock containing the zircon may find itself eroded away or recycled deep into the Earth to be incorporated into newer rocks. While the rest of the rock is lost, zircons tend to survive, becoming part of younger rocks.
This particular zircon became re-incorporated into a rock – an ancient riverbed – that is dated at around 3 billion years old, from the Jack Hills of Australia.
It sounds alarmist, and it is. Someone read something and has jumped to the conclusion that Yellowstone is about to blow (as it did in the movie 2012). Something about too much Helium-4 coming up from the mantle, so, boom!, an eruption is on its way.
Whoever wrote this article doesn’t know a whole lot about geology, or chemistry. Y’know, Helium-4 is the most abundant isotope of helium on the planet. And, yeah, all the helium on Earth comes from the mantle.
There’s no shock here.
Yellowstone is often interpreted as a ‘hotspot’ where magma welling up from the mantle makes its way to the surface. It’s kind of a direct connection with the Earth’s interior. And it’s an active hotspot. So little bits of uplift and the odd earthquake are kind of expected.
But in case you don’t believe me, read this:
You’d think it’d be pretty-much impossible to physically examine Mars rocks in any way here on planet Earth. However, there are a multitude of meteorites on Earth that originally came from Mars. We know they’re from Mars because of their unique chemical signature.
One of these meteorites, called Yamato 000593 (or just Y000593), was cross sectioned and examined under a scanning electron microscope.
The labeled micro-tunnels are similar to those found in Earth-based basalts and are (on Earth anyway) alterations due to biological activity. This is interesting evidence for past life on Mars.