Mars Rover Night Sky Photography

NASA MER Web Site ^ | 3/11/04 | Elk Grove Dan

[ElkGroveDan]

In the most recent MER Spirit PANCAM images you can see that the folks at NASA have decided to start doing some astronomy with the rover cameras.

Below are clips from three nighttime sky pictures from Spirit taken on SOL 67. They were taken using increasingly longer exposures. Astronomers often call pictures like these "star trails." When you take a long exposure with a steady camera, the planet's rotation causes the stars to "trail" across the sky. The longer the exposure, the longer the trails. I used to make these when I was a teenager with my own darkroom, using a camera on a tripod.

Normally all of the stars should trail in the same direction. However if an object "moves" across the sky during the exposure you will get lines that don't trail in the same direction as the stars. A perfect example of this would be an airplane, which would leave a line straight across your star trails.

Also of interest in a star trail photo though, are trails that are left by satellites or asteroids that could move slowly across your photo under the proper conditions. These days on Earth you can't take a star trail without capturing several satellites.

If you look at the three MER night sky photos you will discover two things. One, a bright object that is likely another planet such as Earth or Jupiter as viewed from Mars. I leave it to NASA to tell us later which.

The other thing you will notice (with the help of my arrow) is the trail of an object that has moved across the Martian sky during and between the three exposures. What is it?

On Earth the candidates would be an asteroid or a satellite. On Mars there are three possibilities, an asteroid a satellite or a moon. There are presently three man-made satellites orbiting Mars that I am aware of. The Mars Global Surveyor, The Mars Observer, and the European Space Agency's Mars Express Orbiter.

While Mars has two moons, I suspect that Phobos is not a candidate because as we saw from the recent eclipse photos it would appear much bigger and brighter from the surface of Mars. Deimos does appear much smaller due to its distance, but I have a hunch that it too would look brighter in photos like these.

That leaves one of the three orbiting satellites, whose positions are easy to predict or an asteroid that was inadvertently captured here. My bet is on one of the Mars orbiters, which would be entirely in keeping with some of the other coordinated events NASA has tried on this mission.

[ElkGroveDan]

I'm sure we will hear what the were trying to do witht hese photos later today or tomorrow, but it can't hurt to stimulate some thought and discussion here first.

[ElkGroveDan]

PING

[Sloth]

I suspect that Phobos is not a candidate because as we saw from the recent eclipse photos

Got a link? I must have missed that.

[KarlInOhio]

http://www.freerepublic.com/focus/f-news/1093195/posts

[ElkGroveDan]

http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20040308a.html

[non-anonymous]

4-images superimposed: 1-red, 2-green, 3-blue, 4-magenta (right-click, view image to see full size)

[LibWhacker]

There seem to be lots of other angled streaks of various lengths in your pics. Photographic effects? Wonder if the asteroids in the "asteroid belt" that orbits between Earth and Mars might be more readily visible from Mars than from Earth? Or if the asteroid belt is closer to Mars than to Earth? Anyway, interesting pics, that's for sure.

[non-anonymous]

Since the length of the path is correlated with apparent speed, and the 4 images are taken in close sequence, any "real" non-blinking object has to have a multi-colored connected path.

[Romulus]

likely another planet such as Earth

Smile, everybody!

[LibWhacker]

I had that wrong . . . The asteroid belt orbits between Mars and Jupiter!

[ElkGroveDan]

Rememebr that while the main asteroid "belt" exists between Mars and Jupiter, there are plenty of small bodies THROUGHOUT the solar system in all kinds of orbits.

[Geritol]

Boy am I confused! Why are half the sky objects moving, half not moving? Is the angular velocity of the asteroid belt objects the same as the angular velocity of the planet's rotation? Or are they very bright objects that just blinked once? Or is this an overlay of a time lapse and a more sensitive still?

[Atlas Sneezed]

Since the length of the path is correlated with apparent speed, and the 4 images are taken in close sequence, any "real" non-blinking object has to have a multi-colored connected path.

---

Actually, only a slow moving object would have a multi-colored path. A fast moving track like a meteor would be entirely one color (or two, if it happened at the transition monent between exposures.)

[LibWhacker]

Of course. I was just trying to account for all the non-parallel streaks. Why are we seeing so many? I do not recall seeing that many in any time exposure taken on Earth. Here is a better representation of the asteriod belt. It turns out that it is quite close to Mars and so it seems reasonable to me that in time exposures of the night sky on Mars you would likely capture a few of those asteroids on film.

[ElkGroveDan]

Looks like Opportunity captured another eclipse, this one appears to be Phobos. From teh Opportunity PANCAM Sol 45:

[LibWhacker]

Wow, nice catch, Geritol! I hadn't even noticed that! Photograpic anomalies? I have NO idea.

[Joe Hadenuf]

Great images!

I would love to see the sky "tracked" so the stars would appear still or as points of light without the trails.

Talk about dark, non-light polluted, star filled skies?

[aruanan]

If you look at the three MER night sky photos you will discover two things.

Well, more than two things. In each of the shots there are a bunch of trails that are in different directions from the trails left by the stars.

[Baseballguy]

Those darn Martians.......

[ngc6656]

Were the Earth date and time for these photos provided?