Yes they are potentially. You can have an airship in a near vacuum. Several ideas for balloons for exploring Mars.
This is project Archimedes - a 2009 mission by the German Mars society which never flew.
Also, the Solar Montgolfiere Balloons for Mars
Also, on the Earth, JP Aerospace plan to build orbital airships that are even lighter that would launch from 200,000 feet into orbit. They would accelerate by using ion thrusters and so would no longer be using lift at that stage - after all they have to reach orbital velocity - these are huge airships that are so light they couldn't be built at ground level.
These would be truly orbital airships - and at this point would be in orbit, slowly accelerating to Mach 20 and greater, not floating, but they'd set off from a station at 200,000 feet (60 kms) and at that point would be just floating.
Well, though I don't think they have any such ambition - the atmosphere at this height is roughly comparable to the Mars surface in density. So - if it worked out - such airships could land on the Mars surface and take off directly from the Mars surface, no need for any intermediate steps.
For other ideas for Mars vehicles, various unorthodox and novel ideas, see
Soaring, Buzzing, Floating, Hopping, Crawling And Inflatable Mars Rovers - Suggestions For UAE Mars Lander
This is project Archimedes - a 2009 mission by the German Mars society which never flew.
Also, the Solar Montgolfiere Balloons for Mars
Also, on the Earth, JP Aerospace plan to build orbital airships that are even lighter that would launch from 200,000 feet into orbit. They would accelerate by using ion thrusters and so would no longer be using lift at that stage - after all they have to reach orbital velocity - these are huge airships that are so light they couldn't be built at ground level.
These would be truly orbital airships - and at this point would be in orbit, slowly accelerating to Mach 20 and greater, not floating, but they'd set off from a station at 200,000 feet (60 kms) and at that point would be just floating.
Well, though I don't think they have any such ambition - the atmosphere at this height is roughly comparable to the Mars surface in density. So - if it worked out - such airships could land on the Mars surface and take off directly from the Mars surface, no need for any intermediate steps.
For other ideas for Mars vehicles, various unorthodox and novel ideas, see
Soaring, Buzzing, Floating, Hopping, Crawling And Inflatable Mars Rovers - Suggestions For UAE Mars Lander
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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