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.

[LibWhacker]

However . . . I have seen photographs like that before. I'm trying to remember why astronomers make them . . . No luck yet . . . But I'm still looking for an explanation . . .

[ngc6656]

I checked the linked website. It appears the date and times are not available there.

[ElkGroveDan]

Its a bit complicated, but the objects without trails are very dim stars. As the dim star moves across the sky a small point on the film in the center of the erstwhile startrail gets light the entire time allowing the exposure to build up until enough photons gather to be seen. The points at the beginning and end of the star trail just don't get enough light to show up. Does that make sense?

As for the other small movements in directions different from the star trails that others have mentioned here, I am guessing many of them could be small meteor trails. Mars certainly gets its share of meteors, but since the atmosphere is so thin they probably don't burn up us spectacularly as they do on earth. So I'm guessing those little grains of sand and dust make little winks rather than fiery trails we are accustomed to..

[Pagey]

An "a perfect candidate for The Astronomy Picture Of The Day" BUMP!

[Phil V.]

If you'd like to be on or off this MARS ping list please FRail me

[Brett66]

These trails appear to be at right angles to the planet's rotation which suggests a sattelite in polar orbit. It's either Mars Express or Mars Global Surveyor, maybe a meteorite.

[Monty22]

I wish they had better, color, night cameras so we could see what Jupiter looks like from Mars.

[js1138]

You know the Photoshop healing tool can get rid of all those streaks and make a nice clean image.

[Vermont Lt]

Nah...that was me sneaking home the other night a little later than normal. I had to go home to the mother ship on Europa. I guess we forgot to put the cloaking device on.

No need to stare, move along, nothing to see here.

[ElkGroveDan]

I wish they had better, color, night cameras so we could see what Jupiter looks like from Mars.

From the MER PANCAM it would be just a bright yellowish star, however its range of brighnesses would vary much more than we see from Earth. On occasion it would look brighter than it looks from Earth, and other times it would look much dimmer. You are working with two huge orbits that result in some pretty spectacular distances when they are at opposition from each other.

[Ophiucus]

I was just trying to account for all the non-parallel streaks. Why are we seeing so many?

Here's 2-cents worth - first impression on the larger streak that had the arrow indicators was that it was Phobos. With about a 7.6 hr orbit, it would really move fast in the night sky. Second thought was the orbiter.

As for the other streaks, I'm not sure if the reflectivity of the asteroids or their size would make them that visible. However, with less light pollution and a thinner atmosphere than Earth, I would think that many more "meteor showers" would be visible. It's basically a constant occurrence and my guess is that you could see more in the night sky of Mars than Earth.

[green iguana]

"Boy am I confused! Why are half the sky objects moving, half not moving?"

The dots in the pictures are sensor noise. If you have a digital camera, try taking a very long (30 seconds plus if you can) photo with the lens blocked. The longer the exposure, the more noise is picked up, which is why the three photos get noisier (more and brighter dots) as the star trails get longer.

[ElkGroveDan]

Well Duh. You are probably right.

When I was looking at these I automatically started thinking in terms of film characteristics. Now that I think of it, I haven't done that much interesting with digital photography.

If this is indeed happening, perhaps they should use the stereo camera to take the long exposure images, combine the two and then subtract the unique markings (noise) from each photo.

Its probably time for me to try to pick up a used digital slr from somebody who has moved on to the latest technology. Now that #3 is out of diapers I might be able to afford something on ebay.

[cinFLA]

It's basically a constant occurrence and my guess is that you could see more in the night sky of Mars than Earth

Not.

[ASA Vet]

the "asteroid belt" that orbits between Earth Jupiter and Mars

[ASA Vet]

Opps, sorry. Once again I got caught not reading the entire thread first.

[RightWhale]

They can have Mars. The real bonanza is the Asteroid Belt.

[RightWhale]

could see more in the night sky of Mars than Earth

I would bet you are right. Mars' atmosphere is large, Mars is closer to the Asteroid Belt, and Mars' orbit would be easier to get to from beyond.