Rosetta, Philae and Comet 67P/Churyumov-Gerasimenko.

[Aethon]

IIRC the moon is about 18% reflective- like an asphalt parking lot. Remember, these objects are the cinders from ancient stars. The images you see are overexposed. Normal images would not be informative or interesting.

[sndrtj]

http://blogs.esa.int/rosetta/2014/12/12/comet-67pc-g-in-living-colour/

I don't get it, so it is grey or black?

If you could see it on Earth, it would be pitch black. However, in pictures from space (where this no lighter background!), it would look grey.

[lajoswinkler]

Well not pitch black. Standing on 67P would be similar to standing on a pile of coal. Mind that the appearance of the coal, in the terms of its luminosity, depend on our eyes. They adapt, just like a digital camera does.

[PakledHostage]

Red, green and blue filters. Image was taken on August 6th this year at 120 km distance.

So it's gray. I've tried to boost the saturation, but this is a JPEG so not much can be accomplished. It might have a light green hue, although it's probably just gray to our eyes.

I was curious "how gray" Churyomov-Gerasimenko was in the photo so I used the histogram function in Gimp to plot histograms for the RGB channels in the image. I also plotted the histogram of Lajos' coal heap photo for comparison.

For the benefit of anyone who's not familiar with the details of how it works, computer screens generate colours through a combination of red, green and blue. The data for each image pixel is usually encoded as three 8 bit colour channels and a fourth 8 bit alpha (degree of transparency) channel. Shades of gray result when all three colour channels are equal (e.g. R=87, G=87 and B=87). Black results when all three channels equal 0 and white results when all three channels equal 255. If the image was "perfectly gray", all three colour channels would overlap in the histogram. They don't in either image, although the coal heap has less overlap than the comet. In other words, the portion of the comet image that I analysed is "grayer" than the portion of the coal heap image.

Churyumov-Gerasimenko

Coal heap

[Camacha]

Well not pitch black.

Pretty black nonetheless. Someone from the Rosetta team likened it to darker than a black t-shirt. That's pretty dark, especially in an environment with little light. Even on Earth magicians use black on black cloth to make things disappear.

[lajoswinkler]

Pretty black nonetheless. Someone from the Rosetta team likened it to darker than a black t-shirt. That's pretty dark, especially in an environment with little light. Even on Earth magicians use black on black cloth to make things disappear.

It depends on our eyes. It would be easily visible against the black sky as it's narrow as a light source. On the surface, it would be perfectly easy to see the rocks unless you stare at something white in the same time. Eyes are really great sensory organs.

[Camacha]

It would be easily visible against the black sky as it's narrow as a light source.

I doubt it, since it appear to be one of the reasons these objects are so hard to find when they are far out.

On the surface, it would be perfectly easy to see the rocks unless you stare at something white in the same time. Eyes are really great sensory organs.

They are great, but know limitations. I am not sure what happens when you have a reasonable size sun and that black surface.

[lajoswinkler]

I doubt it, since it appear to be one of the reasons these objects are so hard to find when they are far out.

That literally has nothing to do with how our eyes work. Like, nothing.

They are great, but know limitations. I am not sure what happens when you have a reasonable size sun and that black surface.

Ever been on a fresh asphalt surface? Next time shield your eyes so you can see the asphalt only. It would look something like that. 67P is made of very dark gray rocks, something like fresh, damp coal. Absolutely no problem for looking at.

[Camacha]

That literally has nothing to do with how our eyes work. Like, nothing.

Then what do you mean with "It would be easily visible against the black sky as it's narrow as a light source"? It's a bit cryptic.

Ever been on a fresh asphalt surface? Next time shield your eyes so you can see the asphalt only. It would look something like that. 67P is made of very dark gray rocks, something like fresh, damp coal. Absolutely no problem for looking at.

Except that the environment there is pretty much a lot of black and/or darkness and one blazing bright disk that is sun. That's hard to compare to just standing on some road.

[Aethon]

The view from Philae.

http://www.nasa.gov/jpl/rosetta-orbiter-to-swoop-down-on-comet-in-february/index.html#.VJIZYCvF-Yf

[PakledHostage]

On a lighter note, it seems that French president François Hollande has found Philae, in a manner of speaking.

[PakledHostage]

I just stumbled across this and thought I would share it:

An animation of Rosetta's route from Earth to Churyumov-Gerasimenko in Solar System Scope.

[lajoswinkler]

Here are some sweet close up high resolution photos. One of them seems to be artificially colored.

http://www.esa.int/Our_Activities/Space_Science/Rosetta/Highlights/Comet_close-ups

[Aethon]

I'll hafta quote myself for this one. From post 159, October 3, 2014.

Ok, how about some amateur, dumb guy analysis/questions....

It would be super cool if Cherry/Gerry split in two while Philae is on alive on the surface.

There's a crack forming on comet 67p. Is it braking up?

http://www.universetoday.com/118445/theres-a-crack-forming-on-rosettas-67p-is-it-breaking-up/

[Newt]

It seems entirely possible that it might, as it seems, and has seemed from the start, an unlikely configuration.

If it does, might it break up, and then fuse back together? Could that have happened before?

[NovaSilisko]

That crack's probably been there for hundreds or thousands of years, really. The chances of it splitting just in time for us to have a spacecraft near it are astoundingly small.

[B787_300]

Granted this should be its closest approach to the sun so we will see what happens, it would be really neat though

[Bill Phil]

That crack's probably been there for hundreds or thousands of years, really. The chances of it splitting just in time for us to have a spacecraft near it are astoundingly small.

Not if we, give it some help...

[Tommygun]

A crack.......now we know where Philae's harpoon went.

[Aethon]

http://www.universetoday.com/118444/latest-research-reveals-a-bizarre-and-vibrant-rosettas-comet/

New research on the comet trickling out. Definitely worth a click.

[Magion]

I was bored at school today, so I've done some calculations regarding the possible decapitation of our Ducky's head.

I figured out, that the attractive gravitational force between the body and the head is about 290MN and the centrifugal force caused by the comet's rotation equal to 200MN, so there's only 90MN force pushing those portions together, which might contribute to the disintegration.

Well, let's see if this factor and some outgases can tier Cherry-Gerry apart. I hope it'll, because it'll reveal the otherwise hidden core (and those alien cities underground ).

[moronwrocket]

Anyone else get a very Kerbal feel for how the lander made it to the planet? My early landers used to have the "bounce horizontally and tumble" issue until I massively over SAS'd them. Now I use the Surface navball mode to help cancel sideways acceleration.

http://www.seti.org/weeky-lecture/rosetta-lander-philae-mission-landing-comet-67pchuryumov-gerasimenko

[Sky_walker]

There was a hangout of Matt with Tim Peake https://plus.google.com/events/c653ar3q479sloh89hrphe6hdo0

Important info - Matt confirmed what was discussed earlier on - they will propose for Rosetta to actually land on a comet at the end of it's mission, first slowly spiraling towards the nucleus and than making a touchdown. It's not official yet, but that's the proposal.

It'll allow them to obtain numerous very unique data and again: do something noone ever done before.

Pretty black nonetheless. Someone from the Rosetta team likened it to darker than a black t-shirt. That's pretty dark, especially in an environment with little light. Even on Earth magicians use black on black cloth to make things disappear.

It reflects only 2% of light, it's darker than coal, not just a black t-shirt .

Edited January 28, 2015 by Sky_walker

[epoca]

This is cool. New photos of Philae's dramatic descent and quadruple landing.

[Camacha]

It reflects only 2% of light, it's darker than coal, not just a black t-shirt .

I my experience coal is not that dark, as it tends to shimmer in the right light, but whatever the case: really quite dark.