Social Media Sidebar


Please sign up, comment on articles and bring your friends!

Current poll

PlanetTech is asking:

What do you think about our new web site?

Love it, indeed
Really good solution
Same as old one
The old one was better
This is a new option

Quote of the day

Just because something doesn’t do what you planned it to do doesn’t mean it’s useless.


Thomas Edison

Shooting stars show Earth had oxygen eons before we thought

Posted in Science on 13th May, 2016 11:03 PM by AlexMuller

The remains of 60 micrometeorites have survived 2.7 billion years in the limestone Tumbiana Formation of Western Australia. They are the oldest space rocks discovered on Earth. The fact that the meteorites contain oxides of iron show that the upper part of the atmosphere back then must have contained oxygen.

“We were very surprised to find micrometeorites at all, let alone those with iron oxides,” says Matthew Genge of Imperial College London. “It was incredible, these tiny spherules had trapped ancient atmosphere, storing it away like little treasure chests.”
The biggest surprise was the presence of oxygen, says lead author Andrew Tomkins of Monash University in Australia. “As geologists, we are taught the Earth had no oxygen in its atmosphere before 2.3 to 2.4 billion years ago.”
Several lines of evidence back the idea that Earth’s air only contained minute amounts of oxygen before the so-called great oxidation event some 2.4 million years ago, but crucially they are all based on the composition of the lower atmosphere.
Since the meteorites contain oxygen, it must have been present in the upper atmosphere, some 75 kilometres up. And from the types of oxide minerals in the meteorites, the researchers estimate that levels back then would have rivalled those found in the atmosphere today, roughly 20 per cent.
In fact, the team discovered, atmospheric chemists had predicted that the upper atmosphere on a low-oxygen early Earth would contain a lot of oxygen.
That’s because solar ultraviolet radiation would have split molecules such as water, carbon dioxide and sulphur dioxide, freeing oxygen at high altitudes. The hydrogen released from such reactions would have ended up in space, while elemental sulphur would have fallen to the ground.
Tomkins believes that a methane-rich inversion layer in the middle atmosphere would have inhibited vertical circulation, separating the vast bulk of the anoxic air below from the tenuous oxygen-rich upper atmosphere.
Tomkins hopes to find more meteorite samples from across Earth’s history, to see how the upper atmosphere may have changed, and maybe even when oxygen first appeared.
But this might be a long shot. “It is remarkable that objects as small as the micrometeorites survived intact for 2.7 billion years,” Kevin Zahnle of the NASA Ames Research Centre writes in an accompanying article in Nature.
The survival of iron oxides is particularly unusual, and it may only have happened because of unusually fortuitous circumstances. The lake into which the micrometeorites fell was highly alkaline, with its deepest layers totally anoxic. This is probably what prevented the minerals from dissolving.
“Such conditions are rarely encountered in the geological record, which means that the Pilbara micrometeorites might be a one-off discovery,” Zahnle writes. “But one can wish upon a shooting star.”

Tags: meteoriterockspaceEarthplanetgeologyresearch

Read original article » Back to category


Author: Guest
Posted: 2016-05-14
It is amazing how much about earth's history and its atmosphere remains uncertain and it is this kind of unusual finds that can radically change our hypotheses - very interesting observation Reply
Author: Guest
Posted: 2016-05-14
Finding supporting evidence of such early presence of oxygen also influences our idea about earliest processes linked to life on earth Reply


Recent headlines

  • Posted in Software on 2018-05-26 01:48:47
    From Here to Human-Level AGI in Four Simple more
    Posted in Science on 2018-05-26 01:41:34
    Research Team Builds a Brain Model Neuron By more
    Posted in Hardware on 2018-05-24 04:45:19
    30% Efficiency Solar more
    Posted in Software on 2018-05-24 04:41:49
    Samsung plans AI research centers in Canada, UK more
    Posted in Science on 2018-05-24 04:38:06
    Every 3-5 years SpaceX is adding a decade lead more
Posted in Business on 2013-10-10 01:33
China is working towards a manned lunar mission in more
Posted in Business on 2013-10-20 07:17
Spacex says China is their main competitor for more
Posted in Software on 2013-10-20 06:43
Pirate Bay Browser Clocks 1,000,000 more
Posted in Medicine on 2013-10-10 02:10
Google reportedly investing hundreds of millions into more
Posted in Medicine on 2013-10-14 03:13
Endothelial Cells Can Repair and Regenerate Organs, more
Posted in Science on 01.01.2010
Spacex says China is their main competitor for more
Posted in Science on 01.01.2010
Staring at Your Phone Could Be Making You Short more
Posted in Science on 01.01.2010
Oculus Rift virtual reality headset coming to mobile, more
Posted in Science on 01.01.2010
China is working towards a manned lunar mission in more
Posted in Science on 01.01.2010
Delivering drugs via nanoparticles to target more

Recent Blog Posts

  • Posted by AlexMuller
    In five years quantum computing will be more
    Posted by AlexMuller
    Google partners with Johnson and Johnson to make lower more
    Posted by AlexMuller
    Electron holography microscope with spatial resolution down more
    Posted by AlexMuller
    Lower cost advanced Nuclear power could dominate future US more
    Posted by AlexMuller
    Why Hasn’t AI Mastered Language Translation? more

Login to your Account

Login to your PlanetTech Account here

Remember me

Create a New Account

You just need username and password

The following errors occured:
Verify password:
Remember me