Part of New Horizon's path took it near Mars. Why didn't they use Mars for a gravity speed boost like they did Jupiter? I'm guessing it had to do with the relatively small size of Mars being unable to pull New Horizon due to the probe's speed.


It really wasn't that close, and going out of it's way would have been more trouble than it was worth. See this map from APL of the planets position when New Horizons crossed Mars's orbit.

enter image description here

Looking at the list of objects that New Horizons crossed it's orbit, the only one that even was close enough to consider was the Moon, and as that's never been done, I don't think it was really considered. My educated guess shows it could have added a few hundred m/s to the calculation, but it would have significantly limited the launch window, making it unlikely to be of much use.

  • $\begingroup$ Not only that, New Horizons coudn't wait for a favorable transfer window. It really needed to launch to arrive while Pluto still had an atmosphere. Hence also the fastest launch ever done, crossing the moon's orbit in 9 hours. $\endgroup$ – Joshua Feb 13 '17 at 1:40
  • $\begingroup$ @joshua the freezing of Pluto's atmosphere may not have been the problem. Alan Stern and David Grinspoon, in Chasing New Horizons, mention instead the Southern Hemisphere going into polar darkness due to the dwarf planet's large axial tilt. Putting off the launch would lose more of that hemisphere. See page 71 of the above-referenced book. $\endgroup$ – Oscar Lanzi Apr 13 '20 at 21:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.