Starship Asterisk*

bystander wrote:

aestival wrote:Just looks like something hit at really low, tangential velocity, and was left sitting on the surface -- heck, even looks like it left a bit of a trail on the way in.

I think aestival meant to imply a low incident angle, which might have some merit. It looks like the object could have entered from just above the lower right corner, low to the horizon (like Kaguya), and left something like a wake behind it.

http://en.wikipedia.org/wiki/Iapetus_(moon) wrote:
<<In the 17th century, Giovanni Cassini observed that he could see [Saturn's moon] Iapetus only on the west side of Saturn and never on the east. He correctly deduced that Iapetus is locked in synchronous rotation about Saturn and that one side of Iapetus is darker than the other, a conclusion later confirmed by larger telescopes. The difference in colouring between the two Iapetian hemispheres is striking. The leading hemisphere and sides are dark (albedo 0.03–0.05) with a slight reddish-brown coloring, while most of the trailing hemisphere and poles are bright (albedo 0.5-0.6, almost as bright as Europa). The original dark material is believed to have come from outside Iapetus, but now it consists principally of lag from the sublimation of ice from the warmer areas of Iapetus's surface. It contains organic compounds similar to the substances found in primitive meteorites or on the surfaces of comets; Earth-based observations have shown it to be carbonaceous, and it probably includes cyano-compounds such as frozen hydrogen cyanide polymers.>>

aestival wrote:Just looks like something hit at really low, tangential velocity, and was left sitting on the surface -- heck, even looks like it left a bit of a trail on the way in.

apodman wrote:Correct me if I'm wrong, but in the absence of atmosphere, rockets, or something else to provide braking, I believe you can't hit a planet from outer space with less than that planet's surface escape velocity, which in the case of Mercury is about 4.3 kilometers (about 2.7 miles) per second - which is not "really low velocity" according to most major league pitchers and traffic cops.

apodman wrote:

aestival wrote:looks like something hit at really low ... velocity

Correct me if I'm wrong, but in the absence of atmosphere, rockets, or something else to provide braking, I believe you can't hit a planet from outer space with less than that planet's surface escape velocity, which in the case of Mercury is about 4.3 kilometers (about 2.7 miles) per second - which is not "really low velocity" according to most major league pitchers and traffic cops.

• -------------------------------------------
  _THE THING FROM ANOTHER WORLD_ RKO 1951
  . Screenplay by Charles Lederer
  .......................................
  . NIKKI
  . (opening the note book in
  . her hand and reading from it)
  .
  November 1, 11:15 p.m. Sound detectors
  registered explosion due east. 11:18 p.m.
  magnetic dial revealed twelve point three
  deflection. Such deflection possible only
  if a disturbing force equivalent to 20,000
  tons of steel or iron ore had become part
  of the earth within fifty mile radius.
  .
  . HENRY
  That sounds like a meteor, doesn't it?
  .
  . CARRINGTON (amiably)
  Yes, very much. Except for our photographic
  plates. Our telescopic cameras were working
  last night. Here is the film taken between
  11:12 and 11:15. Let Captain Henry see it, Bill.
  .
  . Stone switches on a light in a moviola box
  . and runs a strip of film slowly through it.
  . Captain Henry looks into the box.
  .
  . CARRINGTON
  You will note the small dot low on the film.
  It is moving from west to east. At 11:14
  the dot moves upward. At 11:15 it drops to
  the earth and vanishes. A meteor might move
  almost horizontally from west to east, but
  never upward. If the traveling object caused
  the explosion we picked up, it is in the ice
  48 miles from here. The sound reached us
  four minutes after the object's disappearance.
  This gives us the approximate distance from here.
  .
  . HENRY (frowning)
  Twenty thousand tons of steel
  is a lot of metal for an aeroplane.
  .
  . CARRINGTON
  For the sort of aeroplane we know, Captain.
  -------------------------------------------

aestival wrote:looks like something hit at really low ... velocity

simonbrueck wrote:Looking at the other craters, it is apparent that there are shadows. The dark material - in my view - could be easily explained by a steeper hill throwing a distinct shadow. The sun does not appear to come from the zenith and mercury´s curvature is not sufficiently narrow to hold up the view, that the craters nearby have shadows and the "dark material" can be straight below the sun.

http://apod.nasa.gov/apod/ap090706.html wrote:
Explanation: What is that strange material on Mercury? When flying by Mercury last October, the robotic MESSENGER spacecraft imaged much of the solar system's innermost planet in unprecedented detail. As common in science, new data bring new mysteries. Pictured above on the lower right, a large crater -- about 100 kilometers across -- has unusual dark material of unknown composition near its center. The material's darkness does not appear to be caused by shadows, as the Sun was near zenith when the image was taken. One origin hypothesis is that the dark material was uncovered from beneath Mercury's surface during the impact that created the surrounding crater. If so, the composition of the dark mound might be similar to the composition of some mysterious dark rings also recently discovered on Mercury. Alternatively, the dark material could be related to an unusual composition of the impacting rock.