Headless Comets Survive Plunge Through Sun's Atmosphere

Science Daily ^ | 6-18-2003 | NASA

[blam]

Source: NASA/Goddard Space Flight Center
Date: 2003-06-18

Headless Comets Survive Plunge Through Sun's Atmosphere

A run through the jungle is too easy; for the ultimate reality show contest, try a race through the Sun's atmosphere, where two comets recently lost their heads. The tails from a pair of comets survived a close encounter with the Sun, even after the Sun's intense heat and radiation vaporized their heads (nuclei and coma), an extremely rare event photographed by the Solar and Heliospheric Observatory (SOHO) spacecraft.

On May 24, 2003, a pair of comets arced in tandem towards the Sun, their paths taking them to just 0.1 solar radii above the Sun's surface, deep within the searing multimillion-degree solar atmosphere (corona).

They belong to the Kreutz family of sun-grazing comets, often seen by the SOHO spacecraft while diving towards their final rendezvous with the Sun. But as in humans, twins are rare. Even more so, this pair showed another very unusual trait: What looks like a faint tail (or "puff of smoke") can be seen moving away from the Sun, seemingly emanating from a point in the orbit beyond the comet's closest approach. Normally, sungrazers simply fade and disappear at an earlier stage, obliterated by the Sun's intense heat and radiation pressure.

Another pair of Kreutz sungrazers with such a "headless tail" was observed in June 1998, when the observing geometry was very similar. But out of more than 600 sungrazing comets observed during more than six years by SOHO, this is only the third showing any signs of such behavior. However, this seems now likely to confirm the existence of such comets.

"Everyone who's seen this agrees it's a very interesting observation," said Dr. Douglas Biesecker, a solar researcher at the National Oceanic and Atmospheric Administration's Space Environment Center in Boulder, Colorado, and the head of SOHO’s comet discovery program. SOHO has become the most prolific comet finder in history.

The tail is most likely the dusty remains of the comet's nucleus, being pushed out by sunlight (radiation pressure) after all the ice in the nucleus has evaporated, thus eliminating the processes maintaining a bright coma surrounding the nucleus. Studies of the dust cloud may reveal clues to the size distribution of the dust grains.

"The fact that the tail 'holds together' so well probably means that the dust is mostly the same size," said Biesecker.

Comets are chunks of ice and dust that zoom around the solar system in elongated orbits. This "dirty snowball" is the nucleus of the comet; it ranges in size from a large boulder to a large city. As the comet gets close to the Sun, solar heat and light liberate gas and dust from the nucleus, forming the coma, which is an extensive, bright cloud around the nucleus, and one or more tails. A comet's dust tail can be millions of miles (kilometers) long and is pushed away from the Sun by sunlight. Comets also have a tail of electrically charged particles (ions) that is usually fainter and is pushed away from the Sun by the solar wind, a thin stream of electrified gas that blows constantly from the Sun. Both tails point away from the Sun, even for comets that are traveling back outwards in the solar system. Studies of the tails can reveal changes in solar wind structure and radiance of the Sun.

SOHO is a project of international cooperation between the European Space Agency and NASA. For images and movies of this event, refer to:

http://soho.nascom.nasa.gov/pickoftheweek/old/27may2003/

Editor's Note: The original news release can be found here.

[blam]

I have a question that I have been contemplating for some time, it is: If a large comet made a close pass to the earth and shed a large amount of water/ice and this water/ice was captured by the gravitational pull of the earth, how exactly would this water/ice reach the surface of the earth? As rain?

[blam]

Ping.

[jigsaw]

"Who knows?" Tom cometed.

[rudypoot]

If the core survived, the impact would destroy it (vaporize). You might see a contrail i think.

[blam]

"If the core survived, the impact would destroy it (vaporize). You might see a contrail i think."

I'm talking about a big comet that has a tail larger than the earth that does not impact. A close pass.

[trebb]

I don't think the gravity well goes all the way to the bottom under a comet. </humor
I would have to think it would reach the surface the same way as any other water/vapor that occurs above the Earth's surface....

[Ernest_at_the_Beach]

I have a question that I have been contemplating for some time, it is: If a large comet made a close pass to the earth and shed a large amount of water/ice and this water/ice was captured by the gravitational pull of the earth, how exactly would this water/ice reach the surface of the earth? As rain?

Wouldn't it just be water vapor and blend in with the other molecules? And might precip out as rain at some point!

[RightWhale]

The tail of the comet is all gas, so the water vapor would mix as vapor with the atmosphere. Eventually it would precipitate out to the ground.

[Pyro7480]

I remember reading that in 1910, the Earth actually passed through the tail of Halley's Comet. The ice particles, since they are moving so fast (tens of thousands of miles per hour) that they would instantly vaporize in the Earth's atmosphere.

[RightWhale]

"The fact that the tail 'holds together' so well probably means that the dust is mostly the same size,"

The dust is probably very fine, like silt. The water ice, once it is free as a kind of dust would evaporate in the vacuum, sublimate.

[blam]

"The dust is probably very fine, like silt. The water ice, once it is free as a kind of dust would evaporate in the vacuum, sublimate."

I'm looking for the cause of the worldwide bibical flood, could something like this be it?

[js1138]

Not likely. You would still be left with the question of where did the water. Perhaps best not to look for naturalistic explanations.

[js1138]

should read: "where did the water go?"

[RightWhale]

If you can imagine the world covered to the tops of the mountains, you must also imagine the water draining somehow. I would be interested in understanding where the water went.

[ffusco]

Melting glaciers?

[ffusco]

It would be interesting to see other cultural references to this worldwide flood.

[Pyro7480]

I don't think so. A comet or asteroid striking one of the oceans could cause A LOT of coastal flooding, and if it broke into fragments beforehand, and the Earth spun a bit before it impacted, it could cause another catastrophic flood.

[Young Werther]

It's the Small Comets, as described by the University of Iowa that have deposited the water on Earth!

SMALL COMETS

I'll have mine on ice with a water chaser!

[Gothmog]

Try the story of Gilgamesh. It is supposedly the oldest ancient epic tale ever recovered (way before the Bible). It is the story of the King Gilgamesh who ruled in Iraq (yep, a little south of Mt Ararat). After his best friend, Enkidu, died, Gilgamesh sought the meaning of life, death and immortality.

He made an attempt to descend into 'hell,' (the seeds of the Greek's Orpheus) but did not get too far. Some old, dusty hole in the ground, ha ha ha.

Then the story relates his long journey in search of his 'father,' an old man who had survived the flood and had the secret of immortality:

"He [Gilgamesh] longed to hear the voice of one
Who still used words as revelations;
He yearned to talk to Utnapishtim,
The one who had survived the flood
And death itself, the one who knew the secret." (source: "Gilgamesh" a verse narrative by Herbert Mason, New American Library (Signet), 1972)

[blam]

"If you can imagine the world covered to the tops of the mountains, you must also imagine the water draining somehow. I would be interested in understanding where the water went."

Maybe not to the top of all mountains.
I was thinking that I've tied a number of catastrophic events to different times and imagery from the bible...and I've always thought that the flood described in the bible was probably the flooding from the end of the Ice Age (or the Black Sea flood) but, that doesn't quite do it.

I'm looking for lots of rain (40 days & 40 nights). The number forty is a mistranslation that should read 'many.' But a lot of rain none-the-less.