Would any of the larger ones be visible with the naked eye? Given that Mars is half an AU closer to the main belt… surely Ceres would be visible, but how about the other biggish ones, like Pallas or Vesta?
Come to think of it… how about some of the planets? Mercury is fairly hard to spot with the naked eye from Earth, how well would it show up from further away? Would Uranus be a naked-eye object?
Vesta is the brightest main belt asteroid as seen from the Earth. It just barely makes it into naked-eye range, at magnitude 5.8 or so. From Mars it would be somewhat brighter, of course, at its closest.
Mercury actually gets quite bright, but it’s close to the Sun, making it difficult to spot sometimes. From Mars it would appear closer to the Sun, and fainter a bit, making it more difficult but I suspect not impossible to spot. I also suspect Earth from Mars would be brighter than Venus from Earth, but I would need to do some hairy math to figure it out. Maybe someone else knows offhand…?
Fascinating question, Steve Wright. I’d like to know the answer too. Bad Astronomer - are you saying we can see at least one of the asteroids from earth with the naked eye ? I’d never have thought it.
I wonder too how Jupiter would look from Mars. I guess the sun would be a little less bright from Mars - would one be able to look at it directly, or would it still be too bright?
According to an Asimov essay I read once, if Jupiter’s brightness didn’t drown them out, you could see the Galilean satellites (Ganymede, Io, Europa and Callisto) with the naked eye.
In a short story by Isaac Asimov (the Missing Item in Casebook of the Black widowers, the good doctor gives the magnitude of objects viewed from Mars. Earth is -4.5 Venus is -2.6 the moon is 0.0 . Earth is brighter. Jupiter is -3.1 Saturn is -1.4. Asimov does not calculate the asteroids.
I did a little digging on the ever-helpful Nine Planets website, and, a few links down, found this table pf absolute magnitudes of the asteroids. If I’m reading it right (I’m only an arts graduate turned computer geek), Vesta (number 4) is a bit brighter than Ceres (number 1), at 3.20 versus 3.34; it’s also about fifty million kilometres closer to the sun than Ceres… so, if we can see Vesta from Earth, it should be no trouble spotting it from Mars… and Ceres might just be visible. If I’m reading this stuff right. Big “if” there.
I don’t know what effect on observation the much thinner Martian atmosphere would have… probably quite significant, given the comments on Earth’s atmosphere in The Bad Astronomer’s book (which is great, btw). OTOH, I suppose I ought to allow my hypothetical Martian observer some kind of breathing gear, which might obstruct his/her vision somewhat.
Thanks for the responses, folks.
There’s something about this on guess who’s website: http://www.badastronomy.com/bitesize/solar_system/jupiter.html
Stupid question, maybe, but… in addition to being 50 million kilometres closer to the asteroid belt on Mars, would you not also have an easier time seeing them by virtue of the thinner, drier atmosphere?
I don’t know if magnitudes take atmospheric effects into account, but surely this would have a significant impact on a ground-based observer’s luck in seeing faint objects.