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For Immediate Release

July 23, 2013

Media Contacts:

Geoffrey Brown, Johns Hopkins Applied Physics Lab, Laurel, Md.
(240) 228-5618 or (443) 778-5618

J. D. Harrington
NASA Headquarters, Washington
(202) 358-5241

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
(818) 354-4673

NASA’s Spitzer Observes Gas Emission from Comet ISON

These NASA Spitzer Space Telescope (SST) images of C/2012 S1 (Comet ISON) were taken on June 13, when ISON was approximately 310 million miles from the sun. The images were taken with SST’s Infrared Array Camera at two different near-infrared wavelengths, 3.6 and 4.5 microns (the false colors shown were selected to enhance visibility). The 3.6-micron image on the left side shows a tail of fine rocky dust issuing from the comet and blown back by the pressure of sunlight as the comet speeds toward the sun (the tail points away from the sun). The image on the right side shows the 4.5-micron image with the 3.6-micron image information (dust) removed, and reveals a very different round structure, the first detection of a neutral gas atmosphere surrounding ISON. In this case, it is most likely created by carbon dioxide that is “fizzing” from the surface of the comet at a rate of about 2.2 million pounds a day.

With a nucleus less than 2 miles in diameter and weighing between 7 billion and 7 trillion pounds, Comet ISON (officially known as C/2012 S1) is, like all comets, a dirty snowball made up of dust and frozen gases like water, ammonia, methane and carbon dioxide — some of the fundamental building blocks that scientists believe led to the formation of the planets 4.5 billion years ago. ISON will pass within 724,000 miles of the sun on Nov. 28, making it a sungrazer comet that will evaporate its ices and even its rocky dust near perihelion, revealing even more of the comet’s composition.

NASA is bringing to bear a vast fleet of spacecraft, instruments, and space- and Earth-based telescopes to study this rarely seen type of comet over the next year. ISON stands for International Scientific Optical Network, a group of observatories in ten countries who have organized to detect, monitor and track objects in space. ISON is managed by the Keldysh Institute of Applied Mathematics, part of the Russian Academy of Sciences.

The complete list of observers is: C. M. Lisse, R. J. Vervack, and H. A. Weaver, Johns Hopkins University Applied Physics Laboratory; J. M. Bauer, Jet Propulsion Laboratory/Caltech; Y. R. Fernandez, University of Central Florida; M. S. P. Kelley, University of Maryland; M. M. Knight, Lowell Observatory; D. Hines, Space Telescope Science Institute; J-Y Li, Planetary Science Institute; W. Reach, USRA/SOFIA; M. L. Sitko, University of Cincinnati; P. A. Yanamandra-Fisher, SSI; K. J. Meech and J. Rayner, University of Hawaii.

Credit: NASA/JPL-Caltech/C. Lisse (JHUAPL)/Y. Fernandez (UCF)

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.

For more information about Spitzer, visit:

NASA’s Comet ISON Observing Campaign:

NASA’s Comet ISON Toolkit:

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