Near-Earth asteroid is really a comet

Sep 10, 2013
The image displays Don Quixote's orbit. Credit: Josh Emery

Some things are not always what they seem—even in space. For 30 years, scientists believed a large near-Earth object was an asteroid. Now, an international team including Joshua Emery, assistant professor of earth and planetary sciences at the University of Tennessee, Knoxville, has discovered it is actually a comet.

Called 3552 Don Quixote, the body is the third largest near-Earth object—mostly rocky bodies, or asteroids, that orbit the Sun in the vicinity of Earth. About 5 percent of near-Earth objects are thought to be "dead" comets that have shed all the water and in the form of that give them their coma—a cloud surrounding the —and tail.

The team found that Don Quixote is neither. It is, in fact, an active comet, thus likely containing water ice and not just rocks. The finding will be presented at the European Planetary Science Congress 2013 in London today, Sept. 10. The discovery could hold implications for the origin of water on Earth.

"Don Quixote has always been recognized as an oddball," said Emery. "Its orbit brings it close to Earth, but also takes it way out past Jupiter. Such a vast orbit is similar to a comet's, not an asteroid's, which tend to be more circular—so people thought it was one that had shed all its ice deposits."

Using the Spitzer Space Telescope operated by the Jet Propulsion Laboratory at the California Institute of Technology under contract with NASA, the team—led by Michael Mommert of Northern Arizona University—reexamined images of Don Quixote from 2009 when it was in the part of its orbit closest to the Sun, and found it had a coma and a faint tail.

Emery also reexamined images from 2004, when it was at its farthest distance from the sun, and determined that the surface is composed of silicate dust, which is similar to . He also determined that Don Quixote did not have a coma or tail at this distance, which is common for comets because they need the sun's radiation to form the coma and the sun's charged particles to form the tail. The researchers also confirmed Don Quixote's size and the low, comet-like reflectivity of its surface.

This is Don Quixote's coma and tail (left) as seen in infrared light by NASA's Spitzer Space Telescope. In after-image processing (right), the tail is more apparent. Credit: NASA/JPL-Caltech/DLR/NAU

"The power of the Spitzer telescope allowed us to spot the coma and tail, which was not possible using optical telescopes on the ground," said Emery. "We now think this body contains a lot of ice, including carbon dioxide and/or carbon monoxide ice, rather than just being rocky."

This discovery implies that carbon dioxide and might be present within other near-Earth asteroids, as well. It also may have implications for the origins of water on Earth as comets may be the source of at least some of it, and the amount on Don Quixote represents about 100 billion tons of water—roughly the same amount that can be found in Lake Tahoe, California's.

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cantdrive85
1 / 5 (16) Sep 10, 2013
This confirms the 'electric comet' theory. The "weakness" of this comet is because it doesn't spend as much time in the far reaches of the solar system as long period comets. It is the eccentricity of orbit of the bodies through the solar electric field which causes this electric discharge.
alq131
3 / 5 (2) Sep 10, 2013
Now, this is the "asteroid" that the new Constellation program would be worthy of capturing and putting in lunar orbit. Though they didn't say its diameter. But 100B tons of water would be a great resource in NEO. Or heck, just site your filling station on it and let it stay in its transjovian orbit allowing some fueling capacity NEO and to Jupiter...if the orbit is in the plane of the ecliptic...
TheGhostofOtto1923
1.8 / 5 (5) Sep 10, 2013
Now, this is the "asteroid" that the new Constellation program would be worthy of capturing and putting in lunar orbit. Though they didn't say its diameter. But 100B tons of water would be a great resource in NEO. Or heck, just site your filling station on it and let it stay in its transjovian orbit allowing some fueling capacity NEO and to Jupiter...if the orbit is in the plane of the ecliptic...
Really? What is the difference between 500 tons and 100B tons, and how do you think the planned mission depicted here
http://www.nasa.g...mission/

-would be able to reach this 500B ton, 19 km diameter rock, surround it with a bag, and redirect it??
HannesAlfven
1 / 5 (14) Sep 10, 2013
It's pretty surreal that two separate articles posted in just a few hours of one another point to bodies that are not thought to be comets on eccentric orbits nevertheless displaying cometary tails. People are treating cometary science like it is a team sport instead of the cosmological rosetta stone that it is. Conventional cometary theory is the least believable piece of our conventional theories, which makes it the proper place to look first when critically questioning our existing astrophysical/cosmological theories.
Torbjorn_Larsson_OM
5 / 5 (6) Sep 10, 2013
What is surreal is the existence of anti-science trolling on science news sites. Most places locks out nuts when they shit on the furniture.
Torbjorn_Larsson_OM
5 / 5 (5) Sep 10, 2013
But the most surreal here is that these nutters take findings that obviously reject their ideas (no discharges et cetera are used to predict the comet activity here), mumbles their mumbo-jumbo which oddly never contains a quantitative prediction matching what we see - so not even wrong, and says "look, it supports us".

Reminds me of criminals when they almost all go around in jail and claim "I'm innocent". Yeah, suuure...
Urgelt
not rated yet Sep 10, 2013
Otto, you are of course correct to say that the planned mission for a 500 ton object would not address the challenges involved in capturing a much larger object.

That's a bit of a quibble, however. Consider: we now know that at least one large cometoid is in NEO. Most of us have been imagining that capture of a comet would require us to go way out and operate on rather longer time-scales. This is a significant discovery! A mission to capture Don Quixote still would be far from trivial, but the payoff could happen much sooner than we had been thinking.

All of those juicy volatiles in Moon orbit would provide a tremendous boost to extending our economic sphere further into space, not so? What we have just learned is that it would be easier to get those volatiles into position for them to be useful than we had previously known. I don't know about you, but I'm excited by the prospect.
moviedream
1 / 5 (2) Sep 11, 2013
Why couldn't we send a manned spaceship to land on this comet, and hitch a ride to Jupiter?
TheGhostofOtto1923
1 / 5 (4) Sep 11, 2013
sphere further
I agree, and this is why we are beginning to experiment at limited scales with visiting them and moving them about. This is only prudent don't you think?
tadchem
not rated yet Sep 11, 2013
Carbon monoxide and water will form a gas hydrate (similar to methane hydrate), which will reduce the sublimation pressure and raise the melting temperature of the water. This could be important to the consideration of the stability of comets that have a perihelion of about 1 AU.
jyro
1.7 / 5 (6) Sep 11, 2013
How big is this thing and when is going to hit California. :)
rug
1 / 5 (6) Sep 11, 2013
Why couldn't we send a manned spaceship to land on this comet, and hitch a ride to Jupiter?
To catch a ride and not use as much fuel? Less we would have to lift and leave more room for other important stuff.
TheGhostofOtto1923
2 / 5 (4) Sep 11, 2013
Why couldn't we send a manned spaceship to land on this comet, and hitch a ride to Jupiter?
To catch a ride and not use as much fuel? Less we would have to lift and leave more room for other important stuff.
You seem to think these things operate under their own power. Once a ship matches their speed and trajectory they would both end up in the same place at the same time whether or not they made contact.

One other possibility might be a miles-long elastic grapple which would accelerate the ship and then wrap itself around the rock to reduce speed and orbit distance. This has actualy been studied as a way of attaching a probe to an asteroid.

The only advantage would be to process fuel and consumables while there.
TheGhostofOtto1923
1 / 5 (3) Sep 11, 2013
Sorry that last sentence should be after the first paragraph. Kim Stanley Robinson explores the potential of using hollowed-out asteroids to travel through the system in his mars series. Again the advantage would be in actually living there while in transit.
rug
1.7 / 5 (6) Sep 11, 2013
Go figure, you called me out on not putting to much thought into it. I admit, Otto got me on that one.

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