Fun thread: what is this a picture of?

[nacnud]

Well this picture seems about the same resolution as the one above, and it came from Mariner 10

 

[najab]

Then I change my answer to Mercury.

 

[teije]

Mercury it must be then. I agree <br /><br />Edit: I never knew that story about the odd orbit that fooled astronomers though. Nice to know. <img src="/images/icons/laugh.gif" />

 

[CalliArcale]

Correct, this is Mercury! It's orbit cannot be predicted by purely Keplerian physics. It takes relativity to predict its orbit. This is because it is close to a very massive object -- the Sun.<br /><br />Fun facts about Mercury:<br /><br />* It is the only planet in the inner solar system which has not been orbited by a space probe; that will change when MESSENGER arrives in orbit. MESSENGER will encounter Mercury twice before entering orbit, using flybys to gradually shift MESSENGER into a trajectory favorable for orbit insertion.<br /><br />* Mercury ought to be the densest object in the solar system because it has a very large core and has a large amount of iron. It loses this distinction to the Earth purely because it is not massive enough to compress itself further. In fact, despite being smaller than Ganymede or Titan, it is more than twice as massive as either.<br /><br />* In addition to its peculiar orbit, Mercury has a peculiar rotation. It rotates exactly three times for every two orbits. This resonance is unique to Mercury. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>