Possible Destination? Researchers Find Water Ice and Organics on Asteroid


We usually think of asteroids as dark, dry, lifeless chunks of rock, just like the image of Asteroid Itokawa, above. But some asteroids may be more like “minor planets” after all. Researchers have found evidence on one asteroid – 24 Themis – of water ice and organic materials. This discovery is exciting on two fronts: one, this evidence supports the idea that asteroids could be responsible for bringing water and organic material to Earth, and two, if the proposed path for NASA is to visit an asteroid, having water and organics at the destination makes things a bit more interesting.

24 Themis, a 200-kilometer wide asteroid sits halfway between Mars and Jupiter. Using NASA’s Infrared Telescope Facility on Hawaii’s Mauna Kea, Josh Emery from the University of Tennessee, Knoxville and Andrew Rivkin of Johns Hopkins University measured the spectrum of infrared sunlight reflected by the asteroid and found the spectrum consistent with frozen water. They determined that 24 Themis is coated with a thin film of ice. They also detected organic material.

“The organics we detected appear to be complex, long-chained molecules. Raining down on a barren Earth in meteorites, these could have given a big kick-start to the development of life,” Emery said.

Finding ice on the surface of 24 Themis was a surprise because its proximity to the sun causes ice to vaporize. Plus, the surface temperatures are too warm for ice to stick around for a long time.

This image shows the Themis Main Belt which sits between Mars and Jupiter. Asteroid 24 Themis, one of the largest Main Belt asteroids, was examined by University of Tennessee scientist, Josh Emery, who found water ice and organic material on the asteroid's surface. His findings were published in the April 2010 issue of Nature. Credit: Josh Emery/University of Tennessee, Knoxville

“This implies that ice is quite abundant in the interior of 24 Themis and perhaps many other asteroids,” Emery said, and therefore the ice is regularly being replenished.

This might be done by “outgassing” in which ice buried within the asteroid escapes slowly as vapor migrates through cracks to the surface or as vapor escapes quickly and sporadically when 24 Themis is hit by space debris.

The discovery of abundant ice on 24 Themis may mean that water is much more common in the Main Belt of asteroids than previously thought. Since Themis is part of an asteroid “family” that was formed from a large impact and the subsequent fragmentation of a larger body long ago, this scenario means the parent body also had ice and has deep implications for how our solar system formed.

Ice on asteroids may be the answer to the puzzle of where Earth’s water came from, Emery said.

“Asteroids have generally been viewed as being very dry. It now appears that when the asteroids and planets were first forming in the very early Solar System, ice extended far into the Main Belt region,” Emery said. “Extending this refined view to planetary systems around other stars, the building blocks of life — water and organics — may be more common near each star’s habitable zone. The coming years will be truly exciting as astronomers search to discover whether these building blocks of life have worked their magic there as well.”

In choosing a possible destination for future explorations, 24 Themis would perhaps be a good candidate.

The findings are published in the April 29 issue of the journal “Nature.”

Source: EurekAlert

9 Replies to “Possible Destination? Researchers Find Water Ice and Organics on Asteroid”

  1. Strange. How is this considered a “new” discovery? A couple of points:
    1) The asteroid shown (Itokawa) is not a “chunk of rock.” It is an example of the “rubble pile” form of asteroid that astronomers have been describing for years. These are loosely packed agglomerations of dust, rock, ICE, and primordial solar system detritus.
    2) The presence of water in asteroids is not a new concept. For example, last year, several main belt asteroids were found to have comet-like tails resulting from ice sublimation. And we’ve known for over a decade that the groundmass in carbonaceous chondrite meteorites is water rich.
    3) Organic compounds have been detected many times in a variety of minor planets.
    It seems to me that this research is more along the lines of “confirmation” rather than “discovery.”

  2. “and two, if the proposed path for NASA is to visit an asteroid, having water and organics at the destination makes things a bit more interesting.”

    Obama Tours …. is boring.

    An Asteriod with some resources that humans would need to live of the land? Well, been there, seen that!

    If heads don’t explode by the pure imagination what could be … then … US human space flight is just a waste of time.

  3. @TerryG

    Is it? From the article I referred to, first sentence: “For the first time, astronomers have confirmed that an asteroid contains frozen water on its surface.”

    I don’t see the difference. Then again, I have not gone in to this too deeply…

  4. @pahles

    You are right.

    Same discovery, same discoverers, different announcements. What seems to have happened is the results made headlines when they where first announced last year and then more recently when the were published in Nature, a reputable scientific journal which is about six months behind other publications.

    Another source, BBC Science on 28th April 2010 http://news.bbc.co.uk/2/hi/science_and_environment/10090128.stm says “Scientists have detected water-ice on the surface of an asteroid. The first-time observation was made on 24 Themis, …”.

    But back in 7th Nov 2009, Science News http://www.sciencenews.org/view/generic/id/48174/title/Ice_confirmed_on_an_asteroid says “Planetary scientists reported October 7 that they have, for the first time, confirmed that an asteroid contains frozen water on its surface. ”

    The discovery actually happened last year. They are the event. Please forgive any confusion I have caused. My apologies.

  5. Well alrighty… I’m finally get it! Low temperature chemosynthesis is an ongoing process in our solar system and is especially noticeable at the distance of the asteroid belt.

    That ‘belt of chemosynthesis’ expands and contracts with Sol’s variable output. If it were to move inward closer than Earth’s orbit, would we have an Ice Age?

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