The comet being observed by Europe’s Rosetta satellite is very gradually spinning down.

The icy dirt-ball takes 12.4 hours to complete one rotation, but mission controllers have noticed that this is extending by about a second a day.

And this rate of change is increasing as Comet 67P gets more active.

“The gas jets coming out of the comet – they are acting like thrusters and are slowing down the comet,” said flight director Andrea Accomazzo.

….During December and January, Rosetta was able to move to within 30km of Comet 67P and go into a gravitationally bound orbit.

This is no longer possible and Rosetta has retreated.

“The aerodynamic effects are now more and more important. The jets are getting stronger and stronger,” the Esa flight director told BBC News.

“To give you an idea, these gases come out of the comet for a few kilometres and are moving at 800 metres per second.

“We definitely have to take this into account. We are a big spacecraft with 64 square metres of solar panels. We’re like a big sail.”

In recent weeks, the dust in the environment around the comet has even confused the star trackers that Rosetta uses to work out its orientation. The trackers thought the dust particles were stars.

Full report: http://www.bbc.com/news/science-environment-31965458

And some recent snaps:

there have been some great pics of this comet.

Space sculpture.

Here’s a recently released false colour image from last year:

False-colour image showing the smooth Hapi region connecting the head and body of comet 67P/Churyumov-Gerasimenko. Differences in reflectivity have been enhanced in this image to emphasise the blueish colour of the Hapi region. By studying the reflectivity, clues to the local composition of the comet are revealed. Here, the blue colouring might point to the presence of frozen water ice at or just below the dusty surface.

Giant Version

The comet’s orbit:

Rosetta has made the first detection of molecular nitrogen at a comet. The results provide clues about the temperature environment in which Comet 67P/Churyumov–Gerasimenko formed.

The graph shows the variation in the signals measured for molecular nitrogen (N2) and carbon monoxide (CO) by Rosetta’s ROSINA instrument. The signals vary as a function of time, comet rotation and position of the spacecraft above the comet. An average ratio of N2/CO = (5.70 +/- 0.66) × 10–3 was determined for the period 17–23 October 2014. The minimum and maximum values measured were 1.7 × 10–3 and 1.6 × 10–2, respectively (note that the ratio cannot be derived directly from this graph – a correction factor accounting for the instrument sensitivity is applied).

By comparing the ratio of N2 to CO at the comet with that of the protosolar nebula, it was determined that the comet must have formed at low temperatures, consistent with a Kuiper Belt origin. The study also finds that Jupiter-family comets like Comet 67P/ Churyumov–Gerasimenko were unlikely the source of Earth’s nitrogen.

Big Version

Cecily is finding this very interesting, especially the diagram of the solar system.

Divine Angel said:

Cecily is finding this very interesting, especially the diagram of the solar system.

That’s encouraging.

Still 143 days to perihelion. I’m hoping that either the comet will break up or Philae will come back to life – ideally both.

> Here’s a recently released false colour image

Excellent. Too many images from Rosetta, Vesta, now Ceres and soon Pluto have been and will be in black and white rather than true colour or enhanced colour. That’s because the scientific cameras are set up for filters in specific wavelengths that don’t closely match what the eye sees. By the way, the latest image of Pluto from New Horizons is 3.4 pixels wide.

This is one of the best things ever

Bubblecar said:

… Rosetta was able to move to within 30km of Comet 67P and go into a gravitationally bound orbit.

This is no longer possible and Rosetta has retreated.

“The aerodynamic effects are now more and more important. The jets are getting stronger and stronger,” the Esa flight director told BBC News.

“To give you an idea, these gases come out of the comet for a few kilometres and are moving at 800 metres per second.

“We definitely have to take this into account. We are a big spacecraft with 64 square metres of solar panels. We’re like a big sail.”

In recent weeks, the dust in the environment around the comet has even confused the star trackers that Rosetta uses to work out its orientation. The trackers thought the dust particles were stars.

Very sensible. Pity though. There was always the chance that the Rosetta spacecraft would be hit by a chunk of disintegrating comet and disabled. It’s still possible and becoming more likely. I wonder how close it will be possible to get at times near perihelion.

mollwollfumble said:

Very sensible. Pity though. There was always the chance that the Rosetta spacecraft would be hit by a chunk of disintegrating comet and disabled. It’s still possible and becoming more likely. I wonder how close it will be possible to get at times near perihelion.

They’re still planning further close flybys. And there’s still some hope they may be able to reboot Philae, the lander:

The science team is, however, preparing some closer flybys.

One of these, in July, could go as close as 20km, and may be used to picture the surface to try to find Rosetta’s lost landing probe, Philae.

The little robot has been unresponsive since losing battery power a couple of days after touching down on 12 November.

Having previously said it would not run another dedicated imaging campaign to try to detect Philae, Esa believes the forthcoming opportunity may actually be quite a favourable one for a search.

Illumination conditions will be much improved at its suspected resting place – certainly, compared with previous campaigns.

Andrea Accomazzo said controllers were now using Rosetta to make radio “shout outs” to Philae, hoping that enough sunshine will soon fall on the lander’s solar panels to reboot it: “The problem is that even if Philae hears Rosetta, it has to have enough charge to turn on its radio transmitter.”

The flight director is a little pessimistic that Philae will get enough energy to come back to life. “I put it at 50-50, but I will be the happiest person in the world if it happens.”

http://www.bbc.com/news/science-environment-31965458