Impact of comets could be responsible for Titan's atmosphere

May 09, 2011 by Deborah Braconnier report
True-color image of layers of haze in Titan's atmosphere. Image: NASA

(PhysOrg.com) -- Titan, Saturn's largest moon, may have had help with the creation of its nitrogen-rich atmosphere, according to a new study published in Nature Geoscience. Scientists believe that multiple impacts by comets hitting the ammonia ice on the moon’s surface converted the ammonia to nitrogen.

Where ’s atmosphere came from has been a long standing question. Was it primordial or did it originate at a later time? In 2005, NASA launched the Huygens probe which ruled out primordial origin based on the low levels of argon-36, an isotope which should show higher levels in a primordial atmosphere.

Another theory was that sunlight could have contributed to the breakup of ammonia into nitrogen; however, this would have required Titan to have formed under high temperatures and differentiate into a rocky core and icy mantle layer. The probe however revealed that Titan was not completely differentiated.

New research, led by Yasuhito Sekine from the University of Tokyo, has found another possible explanation. Around four billion years ago Late Heavy Bombardment filled the solar system with large cosmic impacts. Sekine believes that during this period, Titan was hit numerous times causing the ammonia ice to convert into nitrogen.

With this theory in mind, Sekine set out to test it by using laser guns to fire bullets of gold, copper foil, and platinum at ammonia and ice targets. Propelled by high speed, the bullets hit the targets and the found that this impact was enough to easily convert the ammonia into nitrogen.

Sekine calculated that in order to produce the amounts of nitrogen currently seen on Titan there would have had to have been at least 300 million billion metric tons of impactors which would have been possible during the Late Heavy Bombardment period.

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More information: Replacement and late formation of atmospheric N2 on undifferentiated Titan by impacts, Nature Geoscience (2011) doi:10.1038/ngeo1147

Abstract
Saturn’s moon Titan has attracted much attention because of its massive nitrogen atmosphere, but the origin of this atmosphere is largely unknown. Massive secondary atmospheres on planets and satellites usually form only after a substantial differentiation of the body’s interior and chemical reactions during accretion, yet Titan’s interior has been found to be incompletely differentiated8. Here we propose that Titan’s nitrogen atmosphere formed after accretion, by the conversion from ammonia that was already present on Titan during the period of late heavy bombardment about four billion years ago. Our laser-gun experiments show that ammonia ice converts to N2 very efficiently during impacts. Numerical calculations based on our experimental results indicate that Titan would acquire sufficient N2 to sustain the current atmosphere and that most of the atmosphere present before the late heavy bombardment would have been replaced by impact-induced N2. Our scenario is capable of generating a N2-rich atmosphere with little primordial Ar on undifferentiated Titan. If this mechanism generated Titan’s atmosphere, its N2 was derived from a source in the solar nebula different from that for Earth, and the origins of N2 on Titan and Triton may be fundamentally different from the origin of N2 on Pluto.

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Nydoc
not rated yet May 09, 2011
According to Cassini data, scientists announced on February 13, 2008, that Titan hosts within its polar lakes "hundreds of times more natural gas and other liquid hydrocarbons than all the known oil and natural gas reserves on Earth." The desert sand dunes along the equator, while devoid of open liquid, nonetheless hold more organics than all of Earth's coal reserves.[18] In June 2008, Cassini's Visible and Infrared Mapping Spectrometer confirmed the presence of liquid ethane beyond doubt in a lake in Titan's southern hemisphere.[19]

http://en.wikiped...of_Titan
gunslingor1
not rated yet May 09, 2011
Are you proposing we mine titan and bring all that here? I hope not, that would not only be stupid, but also not feasible.

300 million billion metric tons

-Doesn't that sound a bit high? Oh, tons, that's just a measure of force.
SemiNerd
not rated yet May 09, 2011
Are you proposing we mine titan and bring all that here? I hope not, that would not only be stupid, but also not feasible.

300 million billion metric tons

-Doesn't that sound a bit high? Oh, tons, that's just a measure of force.

Ton is a unit of mass.
Mark_Manning
not rated yet May 09, 2011
To SemiNerd:

Several scientists here on earth have suggested an elevator into space. One that would allow us to send people into space without the usage of fuels. If they are theorizing that, then a pipeline into space to syphon fuels off of other planets really isn't so far fetched. The main question is - how to get to someplace like Titan without using up a lot of fuel in the first place. My thoughts would be along the lines of a magnetic pull system. Think Babylon 5 system only instead of going into hyperspace - it just provides the initial yank towards your destination. No fuel is needed. In the depths of space - super conductive materials could be used so only a small amount of current is needed to get a big shove. The unit then uses its plentiful bounty of fuel from the planet's surface to reset its position. You would have to set up three such stations. One at earth, one at the midway juncture, and one at the final destination.
Quantum_Conundrum
3.7 / 5 (3) May 09, 2011
Are you proposing we mine titan and bring all that here? I hope not, that would not only be stupid, but also not feasible.


It's not feasible as a fuel source, but if you had nuclear rocketry it WOULD be feasible for mining carbon based and nitrogen based resources to Terraform Mars or the Moon, or to provide the carbon and nitrogen for biospheres in orbital platforms.

Since Titan is far less massive than Earth, it's easier to lift off compressed carbon and nitrogen resources from there than from Earth.

Plus, for Terraforming, it makes sense to take resources from multiple uninhabitable objects to make habitations, rather than to take resources from the Earth.

However, this scale of mining and manufacturing in space is at least several decades away, since it requirs far more automation than we have, and requires molecular assembly to be profitable.
Jonseer
1 / 5 (1) May 09, 2011
The irony is rich.

Invest trillions of dollars over decades to develop a system to bring the hydrocarbons on Titan here to use as fuel, INSTEAD of using a fraction of that amount to develop NON-carbon based fuels that are both renewable and do NOT contribute to global warming.

Additionally, while the Earth has always been able to right itself after whatever sudden increase in carbon that results in warming, I can only imagine what would happen if EXTRA carbon were injected into the Earth system. The results wouldn't be pretty. It would turn the silly notion that we could be in danger of a runaway greenhouse effect on Earth from mankind's burning of fossil fuels into a real threat when you add in the tremendous amount of extraterrestrial carbon from Titan.
Nydoc
not rated yet May 09, 2011
"INSTEAD of using a fraction of that amount to develop NON-carbon based fuels"

I'm not silly enough to suggest using Titan for fuel on Earth. Non-carbon based fuels are indeed the way to go. However, they won't reduce the demand for oil completely. Plastics, nylons, synthetic rubber, lubricants, asphalt, wax... the list goes on. Renewable energy isn't going to free us from our need for oil. You certainly wouldn't want to bring hydrocarbons to Earth. Wouldn't it be a better idea to have orbital refineries? Manufactured goods could be delivered anywhere in the world with very little spent to transport them. Then you wouldn't have to worry about contaminating water supplies with manufacturing wastes. It isn't something we can do today, but certainly something to aspire to. Is it possible that Titan could one day pave the way to moving all hazardous manufacturing into space? It might take trillions of dollars and decades to set up, but the benefit to our planet would be enormous.