Rosetta update: comet Churyumov-Gerasimenko is a rubber duckie! (more precisely, a contact binary)

As Rosetta approached its target comet, the shape of the nucleus was revealed to be a contact binary -- two unequal-sized objects in contact with each other:



The whole nucleus measures 4 by 3.5 kilometers, in good agreement with Hubble and Spitzer estimates. It is estimated that the two components would have come into contact at a relative speed of about 3 meters per second in order to stick together in this way.

This unusual shape could present a navigational challenge for the Philae lander team. The Philae navigator Eric Jurado says that "navigation around such a body should not be much more complex than around a nucleus of irregular spherical type, but landing the Philae probe [scheduled for November 11], however, could be more difficult, as this form restricts potential landing zones."

www.planetary.org...

That's one funky comet! I'm very much looking forward to the close-up images by Rosetta. Trying to land a probe on such a body is a problem indeed.

A rubber duckey is right.

Or at least it would have been debunked as such if it were on youtube.

So I have a question. With this new data is it possible for the Comet to split as it approaches our Sun? It seems close enough to me. That could be cool.

I could easily land on that...
I hope I get reincarnated as a bad ass inter-planetary fighter pilot...

a reply to: howmuch4another

They are going in the same direction how would they split?

a reply to: OccamsRazor04

if they are two distinct bodies, then there may be pockets of gas caught between them. or ice.
as it approaches the sun, it will heat and this gas/ice can expand to steam with explosive force.

look at shoemaker-levy 9

originally posted by: okamitengu
a reply to: OccamsRazor04

if they are two distinct bodies, then there may be pockets of gas caught between them. or ice.
as it approaches the sun, it will heat and this gas/ice can expand to steam with explosive force.

look at shoemaker-levy 9

Shoemaker levy fragments traveled in the same path until colliding with Jupiter. It also was not orbiting the Sun at all.

a reply to: OccamsRazor04

In a comet breakup, while the resulting fragments continue on the same general trajectory, the force that dislodged them will send them slowly moving away from each other.

I have no idea about the possibility of this particular comet's breakup (I shall ask around on the astronomy groups and forums), but it would be quite somethig to observe, especially if Rosetta is still there nearby.

~~~

P.S. what I actually came here for, is to post this cool animation of the Rosetta images:



Source: blogs.esa.int...

originally posted by: OccamsRazor04
a reply to: howmuch4another

They are going in the same direction how would they split?

I'm not an expert that's why I asked but a guess would be the ice connecting the masses melts or like OK said gasses expanding rapidly. Add to that the centrifugal force that Wilds animation shows and I would think it possible. I think it's really interesting.

Some estimated facts about the comet:

It's overall density is very low, 102 kg/m3, somewhere between the density of cork and styrofoam. I think this means that there are a lot of voids filled with gas or vacuum. The heating and expansion of this gas could mean the comet might disintegrate. (but let's wait for estimates)

It's escape velocity is just 0.46 m/s, meaning if you jumped hard enough, you would leave the nucleus and not fall back to it. I think that that's the minimum velocity the fragments have to be pushed from each other for the comet to truly come apart.

Latest image from Rosetta, and it looks great! Finally, the "rubber duckie" comet in good resolution: blogs.esa.int...



Enlaged image: www.esa.int...



Also breaking news: Rosetta measured the comet's overall temperature, and it seems to be on the warm side, suggesting that the comet is almost completely covered in dark dust: www.esa.int...

Since quite early images of this comet's nucleus, and persisting through the latest one, I've had the impression that the two lobes are both rather boxy shaped, with some straight edges on one aligned with those on the other. I've looked at a number of images of the nuclei of other comets, but seen nothing similar to this.
The typical comet nucleus appears to be shaped something like a potato, with all the variability that this implies; some elongated, some more nearly spherical, but preserving the same sort of general roundedness.
I've been trying to imagine an astrophysical scenario that would produce a comet of roughly rectilinear shape, without much success.

The low density of this comet has been remarked upon. It is only about 11% as dense as water ice, as against around 60 percent for other comets. Even if we were to disregard the effects of denser materials such as rock and dust, on the whole body density, this means that this comet's interior is made up of at least 89 % essentially empty spaces of one sort or another. This odd, low density may explain why this particular comet happened to be selected for on-site examination by the Rosetta spacecraft.

Here is an even closer view of it, from a different angle.

Reminds me of pulled taffy!



picture from space.com

a reply to: eriktheawful

It's a great picture. There are some very bright (or reflective) areas seen in the recent images. I hope these are patches of ice.

I's been exciting to watch the comet getting closer each day, revealing more detail on the surface. ESA Rosetta blog

By the way, Rosetta's arival and orbital insertion to the comet is tomorrow! The comet's tiny mass means that Rosetta will be able to orbit it any way the mission contol likes, including some funky maneuvers: www.youtube.com...

The appearance of the comet is remarkable, so unlike the rounded, 'potato-shaped' comet nuclei we have seen before. The latest image from the Rosetta spacecraft, now in orbit of the object, reveals two blocky lobes, connected by a rather narrow 'neck' of somewhat sinuous appearance.
On the smaller of the two lobes, and opposite this connection, is a large crater, about half the diameter of this lobe. Given the low density and apparent fragility of the object, it's hard to understand how it survived this impact, intact. Link to article with latest image of the comet, below:
news.sciencemag.org...

originally posted by: Ross 54
The appearance of the comet is remarkable, so unlike the rounded, 'potato-shaped' comet nuclei we have seen before. The latest image from the Rosetta spacecraft, now in orbit of the object, reveals two blocky lobes, connected by a rather narrow 'neck' of somewhat sinuous appearance.
On the smaller of the two lobes, and opposite this connection, is a large crater, about half the diameter of this lobe. Given the low density and apparent fragility of the object, it's hard to understand how it survived this impact, intact. Link to article with latest image of the comet, below:
news.sciencemag.org...

What if this is not a crater, but a site of massive outgassing? Or perhaps it's a crater left by just as fragile body as the comet itself.

Those are both possibilities. Outgassing over a large, highly circular area seems unlikely, though. Melting of subsurface ice and the resultant expulsion of gas is likely to be pretty random. We already know that impacts consistently produce round craters.
As 67 P Churyumov-Gerasimenko is apparently unusually low in density, even for a comet, it seems unlikely that it would encounter another object of similar makeup, from out of the depths of space. The same goes for the suggestion that the object's two-lobed structure was caused by the contact of two similarly constituted objects.

A more recent image, linked below, shows the same area of the comet, from a somewhat different angle. The putative large crater is shown from a much better viewing angle. We see inward sloping walls, from all around the surrounding, elevated terrain, and possible debris piles resting at the bottom of the slopes on the floor of the supposed crater, most conspicuously at about the 4 o'clock position. There also appear to be two fairly distinct dark linear features, which appear to extend across the putative crater.
www.esa.int...