The Rosetta Triangle / Comet 67P/C-G Shoots Cool Jets!

Rosetta’s wild 3-legged orbit around comet 67P/C-G

Now that the Rosetta spacecraft has arrived at the comet, it’s busy following a three-legged triangular orbit. At each apex of the triangle, the probe fires its thruster to turn to follow the next leg of the triangle. Each triangle not only brings Rosetta closer to 67P/Churyumov-Gerasimenko but also serves to measure the comet’s mass. Until we know the comet’s precise mass and center of gravity, the spacecraft can’t enter a direct orbit around it.

Navigation camera image taken on August 7 from a distance of about 52 miles (83 km) from comet 67P/Churyumov-Gerasimenko. Credits: ESA/Rosetta/NAVCAM

While that’s happening, Rosetta has been taking more detailed measurements of 67P’s temperature and found variations across the surface. The warmest spot recorded so far is -63° F (-53° C), very close to the lowest temperature (-60°F) ever recorded in my home state of Minnesota. Still, this is a relatively high temperature especially considering the comet’s great distance from the sun, suggesting that 67P/C-G’s surface is devoid of icy materials, because these compounds are not capable of removing heat.

Two jets shoot vaporized ice and dust from the nucleus of the comet. The bright nucleus had to be overexposed to capture the much fainter jets. Credit: ESA/Rosetta/NAVCAM

MIRO or Microwave Instrument for Rosetta Orbiter has been measuring the amount of ice vaporizing off the comet’s nucleus. If you could somehow gather it up and convert it to liquid, 67P/C-G is releasing the equivalent of two glasses of water a second. Some or much of that water departs in geyser-like fashion as jets seen in the photo above.

Sam Gulkis, principal investigator of MIRO, holds a glass of water to demonstrate that the comet’s now releasing about two glasses of water per second. Credit: ESA/S.Bierwald

Meanwhile, Rosetta is now close enough to its target to study the dust in the coma or comet atmosphere using COSIMA (Cosmic Secondary Mass Analyzer). This Sunday August 10, it will expose the first of 24 target-holders that will collect single dust particles. The instrument will analyze their composition and determine if the material is organic (carbon-containing) or inorganic.

Once collected, the dust will be bombarded with beams of indium ions, kicking ions out of the comet dust. Another instrument called a mass spectrometer will fingerprint and determine the amount of atoms and molecules that make up the dust by analyzing the escaping ions.

An ion, by the way, is an atom that has gained or lost an electron and no longer in its neutral state.

Landing sites are being studied for the November touchdown of the mini-probe Philae, and more detailed images are on their way. Exciting stuff!

Take a close look at this photo of 67P/C-G taken on August 6, 2014. If you look along the left side you’ll see a pattern of interesting striations or layers. Click photo for more information and updates. Credit: Rosetta/Osiris camera

6 Responses

  1. Giorgio Rizzarelli

    Excellent pics again, thanx for sharing the best. I particularly like the composite showing the jet and atmosphere.

    1. astrobob

      You’re welcome! You must be very proud of ESA. I think they’ve done a splendid job. My congratulations!

    1. astrobob

      Hi Andy,
      No electricity needed. They’re caused by solar heating vaporizing ice. In the zero pressure of outer space, ice vaporizes or sublimes directly from solid to vapor when heated by sunlight. That’s why the jets are brighter and much more active when a comet is near the sun and virtually shut off when it’s far.

    1. astrobob

      I doubt it. Comets change with energy input from the sun and other factors like rotation. They gradually lose their ices over time, can become inert and even crumble apart. Entropy rules here too.

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