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There has been much discussion, here and elsewhere about the manned exploration or colonization of Mars. Among the problematic aspects are shortages of hydrogen and nitrogen in most areas, dust, and the problems of landing large vehicles and taking off again.

I was reading the wikipedia article on 1 Ceres and it occurred to me that it is, in many ways, a much better destination. The surface (or immediate sub-surface) appears to contain water, aluminium and magnesium containing minerals and ammonia, as well as unidentified organic compounds containing carbon and sulfur. The escape velocity is only 500 $ms^{-1}$, so relatively little fuel would be needed in early missions, and it would be relatively easy to build an electromagnetic catapult for later missions. Robust cargo could probably be landed by a grazing collision with the surface at close to escape velocity.

So have any studies been done of Ceres as an early target for manned missions, or a medium term target for a permanent base? Are there obvious problems I'm overlooking (compared to Mars, say?)

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  • $\begingroup$ Is there evidence for zero-gee being worse than Mars gravity? $\endgroup$ – Steve Linton Jun 26 '18 at 13:05
  • $\begingroup$ We have some experience with zero gravity but none with Mars gravity. $\endgroup$ – Uwe Jun 26 '18 at 13:47
  • $\begingroup$ With a surface gravity of 0.29 g manned exploration or colonization will be difficult if walking is impossible. There is no fear to reach escape velocity, but it should be possible to avoid unintended jumping. A lot of additional training might be necessary to avoid or minimize health problems. $\endgroup$ – Uwe Jun 26 '18 at 14:29
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There is a lack of solid, science-based study into realistic colonisation options because until Dawn arrived very little was known for certain. Much more is known now but even so, we know probable orders of magnitude more about the Moon/Mars and we still would need more before colonisation could be tackled seriously.

Anything serious that may have been written seems to be in short supply so it's either wild conjecture or, more likely, doesn't exist. I did find some links here but they seem a bit hand-wavey.

https://forum.nasaspaceflight.com/index.php?topic=18832.0

Although asteroids in general have been the subject of some theoretical discussion, generally colonisation has never been addressed and automation proposed as a primary solution.

Ceres is slightly different as you say. It has all the same problems of interstellar transit & habitation as anywhere like Mars and is harder to get to because of distance and the deltaV requirements to enter orbit.

I can see it being a target after Mars for sure, or more likely from Mars. It's easier than Mercury to get to (and stay near), Venus would be limited to an Orbiter and as we go further out distance & radiation become prohibitive with current technology.

The question will be "what reason do we have to send people that robots can't do in our stead?"

Finally, the "grazing landing" you describe at escape velocity is still crashing something into Ceres at ~2000kph. Less of a graze, more of a crater ;)

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  • $\begingroup$ I did say "robust" payloads, but I take the point. $\endgroup$ – Steve Linton Jun 26 '18 at 16:02
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Colonization of Ceres (respectively its surface) is actually not possible because of two main factors related to sleep:

First, a day on Ceres is about 9 hrs 5 min. That is about 3/8 the length of day on Earth. When should astronauts on Ceres go to sleep? When should they wake up? This is an issue that could be avoided by setting a base on a peak of eternal light on one of its poles. I don't know whether Ceres has one but it's possible because Ceres has little axial tilt. That issue however doesn't arise on Mars where the day is about 24 hrs 40 min long which probably is adaptable and if not, astronauts could colonize one of the Martian poles where there is half a Martian year day and the other half there's night and astronauts would live according to the Earth's cycle. So in that matter Mars is easier than Ceres.

The second issue is the very low surface gravity of Ceres: In 0.029 g you have some weight, are falling, are being pulled to the surface, so you need a bed or hammock for sleeping. However in such low gravity you would so easily fall out of bed that you need to tighten yourself to your bed or hammock (which on the other hand would be similar to sleeping in weightlessness). That would make sleeping on Ceres more difficult and uncomfortable than in weightlessness or a high gravity. That is an issue that doesn't arise in the comparably high gravities of the Moon (where the astronauts slept on the ground or in hammocks) and Mars.

So due to the above issues it is impossible to colonize Ceres from my point of view. However it is likely there will be a manned landing on Ceres visiting it for several hours, perhaps by astronauts residing in a spacecraft in Ceresean orbit.

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  • $\begingroup$ On the first point, surely it would be easy enough to use shutters and artificial lighting to simulate any convenient day length. You could either use Earth time, or perhaps a 27 hour day (three Ceres rotations) so that sunlight would be a bit more predictable. Altrernatively, dig in to avoid radiation and just use artificial lighting. On the second, surely a sleeping bag lightly clipped to the floor. $\endgroup$ – Steve Linton Mar 19 at 10:54
  • $\begingroup$ @SteveLinton Well, but as you say it would be clipped and you're extremely light on Ceres but not weightless which results in a difficult sleep. Sleeping in weightlessness is actually very good for REM sleep but on Ceres (and Pallas and Vesta) you're in kind of an intermediate state between weightlessness and strong enough gravity. That makes celestial bodies with that gravities the worst to sleep there, I think. $\endgroup$ – user35272 Mar 19 at 11:37

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