Ceres: The Planet That Wasn't | Hacker News Reader

Ceres: The Planet That Wasn't

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63 pointskostyk24 comments

Why can't we send a rover something similar to Mars Curiosity on Ceres. As water has been detected, it can prove to be a great opportunity for future space explorations. Right now people are totally focusing on Mars but we do need to realize that in order to sustain humans settlement we need lot of water and oxygen. What we really should try to do is choose places where there is lot of water and some basic resources for life so we don't need lot of space just to carry water and basic life supporting resources on space explorations.

The Dawn orbiter just got there. We now have basic surveillance video of all of Ceres. The orbital altitude will be decreased, yielding higher-resolution pictures and more data from other instruments. If there are any interesting places to visit, we should know later this year.

I am aware of the Dawn orbiter. My reasoning for sending a rover is most likely you will be able to collect more details and information. With satellite all you get is high resolution images but if you have a rover you can perform hand on tests on the surface, try drilling and do whatever you are looking to do.

Not sure but wouldn't a rover be difficult to land with the low gravity?

Indeed - surface gravity of 0.029 g and escape velocity of 510 m/s (about 1000 mph) according to wikipedia.

67p was arguably much harder to land on than this would be.

Easier, I would think. The gravity is low enough that you don't need a big rocket to land but high enough that you don't have to worry about bouncing off.

I was thinking about the way they slam the mars rovers into the ground with airbags. That certainly wouldn't work or the rover would bounce around for a long time. But I guess there are other ways. It would certainly be interesting to see what NASA comes up with.

Low gravity makes it easier. No atmosphere means you have to use active deceleration (rockets) rather than parachutes, but it's not going to be worse than Curiosity's "skycrane".

Ceres is big, so the rover can travel only a small distance. Where are the interesting point to visit? Where is the safe terrain to travel? You need a preliminary photograph mission.

Also, the distance from Ceres to the Sun is 1.8 times the distance from Mars to the Sun, so you the solar panels need to be 3 times bigger. (It has almost no atmosphere, so you'll get a bit more light. It has a lower gravity, I suppose it helps to improve the millage, but I'm not sure if the rover will jump too much.)

RTG is a much better solution than solar as Ceres is cold making waste heat useful and increasing RTG efficency somewhat.

https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_...

Long term people could use solar, but nuclear has a lot of advantages is very cold locations.

RTG's are politically tough, people freak out about launching fissile material in a rocket, and for a couple years NASA was in a pinch because we had exhausted remaining plutonium stockpiles (and there were no plans to produce more)

Well put.

Just to backstop that a bit more, Dawn's instruments include a visible/IR spectrometer and a gamma-ray sensor (http://dawn.jpl.nasa.gov/technology/science_payload.asp) which will give us a spatially-resolved map of the surface and near subsurface chemical composition of Ceres.

The resolution of these maps will increase as the orbiter is able to descend to lower altitudes (~375km from its current ~1400km; in late July it was still at 2400km). Performing the descent properly requires knowing about Ceres' gravity field, the modeling for which is happening now, as we learn more about the gravity field. Navigation for this mission was very challenging. Landing would require even more detailed gravity information, as well as chemical information for site selection.

But don't think landers and rovers are not being considered. It's all about ranking in the Decadal Survey, conducted regularly for all planetary missions by the National Academy of Science (https://en.wikipedia.org/wiki/Planetary_Science_Decadal_Surv...). As you can see by visiting the link, there is a lot of competition.

A brief piece surveying Ceres research submitted to the last decadal survey (http://www.lpi.usra.edu/decadal/sbag/topical_wp/AndrewSRivki...) contains this:

"A landed mission is an obvious subsequent step for the study of Ceres. Such a mission, whether a Phoenix-type lander or a MER-type rover, will provide a critical link between the remote sensing available from the ground and from Dawn and geochemical studies performed in earthbound laboratories. [...] The specific case for such an advanced mission will probably have to wait until the return of Dawn data, but Dawn’s Ceres phase occurs early in the time period considered here, and it is not too early to prepare for such an mission so that we may expeditiously take advantage of Dawn’s findings."

In other words: what Animats said, but longer. ;-)

We can do that. Which other missions do you want to cancel? How does having a rover on Ceres help make progress towards having human settlements? Are there more cost effect ways to get there?

Personally, I think the money would be better spent on artificially closed ecosystem projects like MELiSSA than on a rover.

I'm not sure if you were suggesting Ceres as an alternative to Mars, but there's plenty of water on Mars.

I guess the nice part about Ceres is the low gravity. A settlement there would be able to easily use its resources for further space exploration or whatever. And people could get home more easily.

One local gravity advantage is its obviously easier to structure and pile 3 meters of soil for micrometeor protection and thermal stability or whatever the standard is. If you're going to dig and pile up dirt as part of building your settlement, may as well do it low gravity.

Other than the distance thing, it would be a pretty awesome settlement location.

If you want a microgravity settlement a near-Earth asteroid would be more convenient - or just a space station. But microgravity is not good for the health of people living there.

Those may be a little too micro. Maybe an artificial gravity space station that slowly orbits Ceres :) Now we're getting crazy. But really, that may be an optimal setup.

That's a pretty big jump between Ceres' small but still significant gravity and being in total freefall. Granted, Ceres is pretty tiny compared to Mars or even the Moon, but we don't know at what point on the spectrum between "microgravity" and "Earth" do we see noticeable health risks. Maybe we're finely tuned for Earth gravity, and we'll suffer even on Mars. Maybe it's just the freefall that's the most harmful, and that any gravitational sense of "down" will be healthy enough for a settlement to actually be viable. Some long-term lunar habitability experiments would be a good first step to finding that point.

If asteroid mining starts to catch on, Ceres would be a really nice spot for staging mining expeditions, materials processing, etc. Combined with the abundance of water ice, it could be even more ideal of a colonization target than even Mars, especially if the effects of longterm exposure to its lower gravity can be identified.

>noticeable health risks

There might also be a continuum and people living in freefall need to exercise 9 hours a day to live long term, but on Ceres its only 3 hours a day, so there's an interesting economic labor argument WRT 6 saved labor hours per day, or whatever the numbers work out to.

I imagine it be easier to fake earth-like gravity on a station above a planet (say a rotating wheel space station) than on the planet. Would a space elevator be possible somewhere like Ceres with lower gravity / atmosphere? If so, it would be much easier to resupply water and materials.

I'm sure a space elevator would be easy on Ceres, but with gravity like that, why bother? An electromagnetic launcher could be pretty small there, maybe even small enough to launch people without too much effort. Or regular rockets, since something very small would be able to escape.

I wonder if whether or not this is the right question. What if we asked the question "Do we want to commit to being able to explore the solar system?" and if we do, what infrastructure could we build in orbit and/or on the moon that would support that activity?

The current one mission - one budget (I know it isn't quite that bad, but it seems close to that) is not sustainable. I'd love to see us build on orbit refueling depots, that would let us launch to LEO at any time, then refuel, and have plenty of gas to get to where ever we want to go. What's more we send automated fuel depots into orbits around remote planets and they let you top up once you get there. Does that allow us to use the same hardware to do several explorations?

Imagine building a space tug that would sit in orbit until you want to send a rover to Ceres to check it out, you launch a rover and its 'landing system' (be it airbags, a rocket crane, or just thruster packs) on a reusable Falcon 9 for basically the price of gas to get the F9 to LEO. It then rendevous with the tug, which fills up with fuel and adds the delta-V to put you into an intercept with the target. Once there the lander/crawler is dropped off, the tug refills at the local fuel depot, and boosts back to Earth.

Large initial investment to put infrastructure off planet, but then that infrastructure enables exploration at a much lower marginal cost.

Totally agree with what @ChuckMcM. My initial comment was for a long term vision but I guess people don't think its a cool idea. Also for all who are all excited about Mars it is not that simple to produce water. You will have to grind the soil into fine particles, heat it and then collect the vapor and condense it. While you have lots of traces of water already present on Ceres why not use that? Also Ceres is at a reasonable distance it's not like you are going to Pluto.

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