Comet ISON Caught Passing Gas, Soda-Pop Comet Is Fizzing

These images from NASA’s Spitzer Space Telescope of C/2012 S1 (Comet ISON) were taken on June 13, when ISON was 310 million miles (about 500 million kilometers) from the sun.

Image Credit: NASA/JPL-Caltech/JHUAPL/UCF

“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.

Comet ISON as imaged by Hubble in May 2013

Credit: Hubble Space Telescope

“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 now approaching the inner solar system. Discovered last year, the comet remains unusually active for its distance from the sun. If current trends continue, ISON could rank as one of the brightest comets in decades when it makes its close approach to the sun in late November. This animation shows the comet’s approach and departure from the inner solar system from various perspectives.

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.”

On April 30, NASA’s Hubble Space Telescope observed Comet ISON. Here we see the comet splashed out over deep space, in a collage with colorful, distant neighbors.

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.

Contacts and sources:

Jet Propulsion Laboratory

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