Pew! Rosetta’s Comet Has Bad Case Of Gas, Halitosis

Comet Churyumov-Gerasimenko’s jets of gas and dust shoot high above its surface into space in this photo taken on September 10 and released this week. As the comet slowly approaches the sun, scientists are seeing these dusty geysers all over the comet, not just the neck region. Click to enlarge. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/ INTA/UPM/DASP/IDA

I count at least 20 individual jets in this recently released photo of comet 67P/Churyumov-Gerasimenko. No doubt about it. As the comet wends its way toward the Sun, there’s been a clear increase in outgassing. Early photos showed several jets – pillars or geysers of rapidly vaporizing ice laden with dust and organic compounds – leaving the narrow neck of the comet. Scientists are now seeing jets everywhere on the icy nucleus. Like a bad pipe, the comet is springing leaks all over!

Close up of the comet taken on October 20 from a distance of just 4.6 miles (7.4 km). The frame is about 2,116 feet (645-m) across. Click to see a larger version worthy of a few minutes of armchair exploration. Credit: ESA/Rosetta/NAVCAM

“At this point, we believe that a large fraction of the illuminated comet’s surface is displaying some level of activity,” says OSIRIS scientist Jean-Baptiste Vincent from the Max Planck Institute for Solar System Research in Germany.

Photographing jets means the much brighter comet nucleus has to be overexposed, the reason all the detail is washed out. 67P is now 292 million miles (470 million km) from the Sun or about three times Earth’s distance. Based on past comet behavior, jet activity should kick into high gear when it comes within 186 million (300 million km) of the Sun. That will happen in March 2015.

Another view of the comet from the same 4.5 mile distance. The frame is also 2,116 feet (645-m) across. Credit: ESA/Rosetta/NAVCAM

The material shot out by the comet goes to create a mini-atmosphere around it called a coma. Since early August, the Rosetta Orbiter Sensor for Ion and Neutral Analysis (ROSINA) has been ‘sniffing the fumes’ of 67P/C-G with its two mass spectrometers. This device identifies molecules produced by the comet by how much their paths are deflected by a magnetic field generated by the instrument. Lighter particles are deflected more than heavier ones.

It appears Comet Churyumov-Gerasimenko has a bad case of halitosis. If you could be there to sniff it yourself, you’d recoil at the smell of rotten eggs mixed with ammonia (think soiled kitty litter) and the pungent pickle tang of formaldehyde. Here’s how Kathrin Altwegg, principal investigator for ROSINA, put it:


High resolution mass spectrum from ROSINA taken on October 10 at a distance of  6.2 miles from the comet center. The plot shows the detection of hydrogen sulphide and the heavier isotope of sulphur, 34S. The plot shows intensity vs. the mass-to-charge ratio. Image courtesy K. Altwegg, University of Bern

“The perfume of 67P/C-G is quite strong, with the odor of rotten eggs (hydrogen sulphide), horse stable (ammonia), and the pungent, suffocating odour of formaldehyde. This is mixed with the faint, bitter, almond-like aroma of hydrogen cyanide. Add some whiff of alcohol (methanol) to this mixture, paired with the vinegar-like aroma of sulphur dioxide and a hint of the sweet aromatic scent of carbon disulphide, and you arrive at the ‘perfume’ of our comet.”

Using ROSINA, here’s a list of what’s been detected as of October 23.

Water (H2O)
Carbon monoxide (CO)
Carbon dioxide (CO2)
Ammonia (NH3)
Methane (CH4)
Methanol (CH3OH)
Formaldehyde (CH2O)
Hydrogen sulphide (H2S)
Hydrogen cyanide (HCN)Sulphur dioxide (SO2)
Carbon disulphide (CS2)

The first three ingredients on the list make up most of the volatile (prone to vaporize) portion of the the comet. Wouldn’t it be nice to have a chunk of 67P in a bottle where you could lift the lid and take a sniff now and again? Naw, come to think, my wife wouldn’t want that in the house.

7 Responses

  1. Edward O'Reilly

    On the CTV news ticker here in Canada,one of the chemical analogues listed was horse urine! Don’t know if some wiseacre got hold of the news feed,but,if true,I sense a name change coming for Comet 67P! lol

  2. caralex

    Bob, are the photos in the blogs below of Comet Siding Spring the best we’re going to get? Will there be any others?

    1. astrobob

      If you’re talking about spacecraft, they may be. I haven’t heard of more though I contacted JPL and asked them to alert me when anything from Curiosity showing the comet becomes available.

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