# How close to the planet Mars would an object have to be to generate friction in its atmosphere?

If satellites were in place with space elevator type cable holding a "friction generator" close to the Martian atmosphere, how far from the surface would the said device have to be? I don't need an exact answer. I am wondering if such a device might be seen with the naked eye while standing on the planets surface.

The improbability of such a device is not in question at the moment. Thank you.

• How much friction is needed? Enough for aerodynamic effects to turn a turbine? If so, a good estimate might be the martian karman line. – Paul Jan 7 '18 at 22:35
• I don't have time to investigate deeply enough for a real answer, but there may be a paper on the Oct 19 2014 MAVEN observations of a meteor shower on Mars containing data that would indicate the altitudes meteors would be observed at. I think it's a fair assumption that altitude is a good lower-bound for causing some dangling cable to make a visible trail. Not clear to me if meteors have ever been seen from the surface of Mars yet. – Erin Anne May 4 '18 at 6:09

Of course the second I comment that I won't research it...

The page Martian Meteor Showers repeats a claim that the altitude for, and magnitude of, meteors on Mars are roughly the same:

A 1996 paper in the journal Icarus by Adolfsson, Gustafson and Murray has pointed out that, although the atmospheric pressure at the surface is less than one percent the respective value at the Earth, the larger mean scale height of the atmosphere means that at an altitude of ~120km where meteoroids begin to ablate, atmospheric densities are comparable. As a result, meteors of the same mass and atmospheric entry speed at the atmospheres would be of similar magnitude . Taking into account the slower average speed of incoming material at the heliocentric distance of Mars from the Sun, a meteoroid of the same mass entering the martian atmosphere at 30km/sec would produce a meteor +0.5 mag fainter than at Earth.

So, 120km and yes, it could be visible.

Adolfsson, Gustafson and Murray, The Martian Atmosphere as a Meteoroid Detector Icarus, Volume 119, Issue 1, January 1996, Pages 144-152, https://doi.org/10.1006/icar.1996.0007

• Bravo! for the find! I'm not sure an answer about meteor visibility is exactly an answer to the OP's question though. It's about some kind of space elevator and "friction generator" mechanism, and if that device would be visible based on it being at the proper operational altitude. It would be better if there were a question... "Of course, the second I comment...": What will shooting stars look like on Mars? – uhoh May 4 '18 at 6:43
• yeah, it's a bit of a stretch, but I've found that starting out with dumb analogies is sometimes illuminating. :) – Erin Anne May 4 '18 at 18:36
• I wrote What will shooting stars look like on Mars? specifically for you, can you consider copy/pasting this as a answer there as well? – uhoh May 4 '18 at 19:56
• this is why nobody writes things for me. Done. – Erin Anne May 4 '18 at 22:45