[b0g]

http://www.esa.int/Our_Activities/Sp..._in_comet_coma

2 June 2015

Rosetta’s continued close study of Comet 67P/Churyumov–Gerasimenko has revealed an unexpected process at work, causing the rapid breakup of water and carbon dioxide molecules spewing from the comet’s surface.

ESA’s Rosetta mission arrived at the comet in August last year. Since then, it has been orbiting or flying past the comet at distances from as far as several hundred kilometres down to as little as 8 km. While doing so, it has been collecting data on every aspect of the comet’s environment with its suite of 11 science instruments.

One instrument, the Alice spectrograph provided by NASA, has been examining the chemical composition of the comet’s atmosphere, or coma, at far-ultraviolet wavelengths.

At these wavelengths, Alice allows scientists to detect some of the most abundant elements in the Universe such as hydrogen, oxygen, carbon and nitrogen. The spectrograph splits the comet’s light into its various colours – its spectrum – from which scientists can identify the chemical composition of the coma gases.
Rosetta’s imaging and spectroscopy instruments
Access the video

In a paper accepted for publication in the journal Astronomy and Astrophysics, scientists report the detections made by Alice from Rosetta’s first four months at the comet, when the spacecraft was between 10 km and 80 km from the centre of the comet nucleus.

For this study, the team focused on the nature of ‘plumes’ of water and carbon dioxide gas erupting from the comet’s surface, triggered by the warmth of the Sun. To do so, they looked at the emission from hydrogen and oxygen atoms resulting from broken water molecules, and similarly carbon atoms from carbon dioxide molecules, close to the comet nucleus.

They discovered that the molecules seem to be broken up in a two-step process.

First, an ultraviolet photon from the Sun hits a water molecule in the comet’s coma and ionises it, knocking out an energetic electron. This electron then hits another water molecule in the coma, breaking it apart into two hydrogen atoms and one oxygen, and energising them in the process. These atoms then emit ultraviolet light that is detected at characteristic wavelengths by Alice.

Similarly, it is the impact of an electron with a carbon dioxide molecule that results in its break-up into atoms and the observed carbon emissions.

“Analysis of the relative intensities of observed atomic emissions allows us to determine that we are directly observing the ‘parent’ molecules that are being broken up by electrons in the immediate vicinity, about 1 km, of the comet’s nucleus where they are being produced,” says Paul Feldman, professor of physics and astronomy at the Johns Hopkins University in Baltimore, and lead author of the paper discussing the results.

By comparison, from Earth or from Earth-orbiting space observatories such as the Hubble Space Telescope, the atomic constituents of comets can only be seen after their parent molecules, such as water and carbon dioxide, have been broken up by sunlight, hundreds to thousands of kilometres away from the nucleus of the comet.

[b0g]

have I posted the Philea photo of its place on the 67P?

[b0g]

Comet Lander Philae Wakes Up After Months of Hibernation

Andrew Katz Katz

ESA 9:05 AM ET 14/6/2015
esa probe philae

The comet lander "spoke" for 85 seconds via its orbiter, "Rosetta"

The comet lander that went into hibernation last last year has made contact with its team back on Earth, European space officials said on Sunday.

In a brief and excited statement, the European Space Agency said the unmanned Philae, which landed on 67P/Churyumov-Gerasimenko in November to become the first spacecraft to touch down on a comet, sent a number of signals via its orbiter (“Rosetta”) to an operations center in Darmstadt, Germany. They were received on June 13 at 10:28 p.m., local time.

Dr. Stephan Ulamec, Philae Project Manager at the German Aerospace Center (DLR), said “Philae is doing very well.” The comet lander “spoke” for 85 seconds, the statement continued, and appeared to have been awake prior to sending the signals, as it transmitted “historical data” as well.

After November’s historic landing, officials said Philae had settled in a spot where it didn’t receive as much sunlight as necessary, causing its battery life to drain.

[lkduke3]

This is so cool, you guys. Thank you for taking the time to post it.

[hal0mega]

You could almost imagine planets being eggs, and comets the sperm that fertilizes them!

[b0g]

MIRO instrument made a first map of water in the coma of 67P
http://wp.me/p46DHN-1gt

[Desensitisation]

Whilst it didn't land where it was supposed to, it seems that has ended up being a blessing. Originally, the lander would have burned out with the continued exposure to sunlight after a few weeks. Now it seems it might keep sending information, albeit slowly, over several months. Cool beans.

[b0g]

Still u missed a troubling fact: as the comet nears the sun it'll spew out more and more dust and gasses, so it interferes badly with the comm signals. so mission center has realligned, and s till is, Rosetta for capturing the least dust mist (fysical stuff) and halo (all the EM waves incl visual). it is a compromise btw signal reception and Rosetta bn able to get nice pics.

[b0g]

concrete: Rosetta has moved away from the comet (15 km and now +100 as I last saw a week ago) so the signal from Philea gets lots weaker!!! due to the power sequence r²=I
maybe we have already had the optimum.

[b0g]

And also for spoiling your party: all pictures of 67P¨are digitally brightened! It is really a dark place and a dark object.
Think of it as watching these pics with 2 or 3 sunglasses on on top of each other.
That's reality.