[meteorite-list] NASA'S Spitzer Observes Gas Emission From Comet ISON

[Ron Baalke]

July 23, 2013

J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington at nasa.gov 

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-4673
whitney.clavin at jpl.nasa.gov 

Geoffrey Brown
Johns Hopkins Applied Physics Laboratory
240-228-5618
geoffrey.brown at jhuapl.edu 

RELEASE 13-229

NASA'S Spitzer Observes Gas Emission From Comet Ison

WASHINGTON -- Astronomers using NASA's Spitzer Space Telescope have observed  
what most likely are strong carbon dioxide emissions from Comet ISON ahead of  
its anticipated pass through the inner solar system later this year.

Images captured June 13 with Spitzer's Infrared Array Camera indicate carbon  
dioxide is slowly and steadily "fizzing" away from the so-called "soda-pop  
comet," along with dust, in a tail about 186,400 miles long.

"We estimate ISON is emitting about 2.2 million pounds of what is most likely  
carbon dioxide gas and about 120 million pounds of dust every day," said  
Carey Lisse, leader of NASA's Comet ISON Observation Campaign and a senior  
research scientist at the Johns Hopkins University Applied Physics Laboratory  
in Laurel, Md. "Previous observations made by NASA's Hubble Space Telescope  
and the Swift Gamma-Ray Burst Mission and Deep Impact spacecraft gave us only  
upper limits for any gas emission from ISON. Thanks to Spitzer, we now know  
for sure the comet's distant activity has been powered by gas."

Comet ISON was about 312 million miles from the sun, 3.35 times farther than  
Earth, when the observations were made.

"These fabulous observations of ISON are unique and set the stage for more  
observations and discoveries to follow as part of a comprehensive NASA  
campaign to observe the comet," said James L. Green, NASA's director of  
planetary science in Washington. "ISON is very exciting. We believe that data  
collected from this comet can help explain how and when the solar system  
first formed."

Comet ISON (officially known as C/2012 S1) is less than 3 miles in diameter,  
about the size of a small mountain, and weighs between 7 billion and 7  
trillion pounds. Because the comet is still very far away, its true size and  
density have not been determined accurately. Like all comets, ISON is a dirty  
snowball made up of dust and frozen gases such as water, ammonia, methane and  
carbon dioxide. These are some of the fundamental building blocks which,  
scientists believe, led to the formation of the planets 4.5 billion years  
ago.

Comet ISON is believed to be inbound on its first passage from the distant  
Oort Cloud, a roughly spherical collection of comets and comet-like  
structures that exists in a space between one-tenth light-year and 1  
light-year from the sun. The comet will pass within 724,000 miles of the sun  
on Nov. 28.

It is warming up gradually as it gets closer to the sun. In the process,  
different gases are heating up to the point of evaporation, revealing  
themselves to instruments in space and on the ground. Carbon dioxide is  
thought to be the gas that powers emission for most comets between the orbits  
of Saturn and the asteroids.

The comet was discovered Sept. 21, roughly between Jupiter and Saturn, by  
Vitali Nevski and Artyom Novichonok at the International Scientific Optical  
Network (ISON) near Kislovodsk, Russia. This counts as an early detection of  
a comet, and the strong carbon dioxide emissions may have made the detection  
possible.

"This observation gives us a good picture of part of the composition of ISON,  
and, by extension, of the proto-planetary disk from which the planets were  
formed," said Lisse. "Much of the carbon in the comet appears to be locked up  
in carbon dioxide ice. We will know even more in late July and August, when  
the comet begins to warm up near the water-ice line outside of the orbit of  
Mars, and we can detect the most abundant frozen gas, which is water, as it  
boils away from the comet."

NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., manages the  
Spitzer Space Telescope mission for NASA's Science Mission Directorate in  
Washington. Science operations are conducted at the Spitzer Science Center at  
the California Institute of Technology (Caltech) in Pasadena. Data are  
archived at the Infrared Science Archive housed at the Infrared Processing  
and Analysis Center at Caltech. Caltech manages JPL for NASA.

For more information about Spitzer, visit:

http://www.nasa.gov/spitzer 

Learn more about NASA's Comet ISON Observing Campaign:

http://www.isoncampaign.org 

NASA's Comet ISON Toolkit:

http://solarsystem.nasa.gov/ison 

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