Mercury Landers Options

[gndonald]

While the likelyhood of a Mercury Lander mission is very low, I was wondering if any planning/studies have been done on such a project?

[Patteroast]

The European 'BepiColumbo' mission planned for the next decade included a lander at once point, but it was cut. I believe this mission also included multiple orbiters and a collaboration with JAXA... but I'm not sure off the top of my head.

I don't see why it would be particularly difficult.. as long as it landed either during the day or the night.. I can't imaging a spacecraft withstanding the temperature difference between them.

[Bob Shaw]

The European 'BepiColumbo' mission planned for the next decade included a lander at once point, but it was cut. I believe this mission also included multiple orbiters and a collaboration with JAXA... but I'm not sure off the top of my head.

I don't see why it would be particularly difficult.. as long as it landed either during the day or the night.. I can't imaging a spacecraft withstanding the temperature difference between them.

The problem isn't so much the engineering - a nice vaccuum, and abundant solar power are hardly the worst-case scenarios for a spacecraft - but the Delta-V requirements. Mercury is an expensive place to reach, and is substantially bigger than the Moon, so you have to expend more effort once you get there.

Personally, I'd leave it until some alternative propulsion method was found - solar/ion engine, Prometheus, solar sail, whatever.

[djellison]

Impactor could work

Doug

[Guest_BruceMoomaw_*]

ESA studied alternative possible designs for a BepiColombo lander in great detail, until they concluded that they just didn't have the money. Meanwhile, the US has pretty firmly concluded that a Mercury multiple-small-lander mission is the only logical next step after Messenger and BepiColombo, although it's not all that high on NASA's Solar System priority list. (It would likely be a New Frontiers-class mission, costwise.)

[remcook]

Although the Bepi-Colombo lander is cancelled, ESA has spend some money on studies. So there are people building stuff that won't actually fly...

[djellison]

Well - studies dont equal flight hardware. Maybe some simulations, maybe some studies, some spreadsheets - but I doubt a single bit of metal was cut.


Doug

[remcook]

actually, hardware is actually made at this moment. However, they will make it such that it is also possible to use it on Mars, very conveniently

[JRehling]

The problem isn't so much the engineering - a nice vaccuum, and abundant solar power are hardly the worst-case scenarios for a spacecraft - but the Delta-V requirements. Mercury is an expensive place to reach, and is substantially bigger than the Moon, so you have to expend more effort once you get there.

Personally, I'd leave it until some alternative propulsion method was found - solar/ion engine, Prometheus, solar sail, whatever.

Mercury ends up being a fairly challenging target for a lander. Of course, the delta-v needed to get *anything* there is a problem. But even when that hurdle has been cleared, it is the hardest place in the inner solar system to land on. Because it has no atmosphere, all of the braking has to be done with thrust. Unlike the other inner-solar-system world in that category, the Moon, Mercury's got some real gravity -- about same g/escape velocity as Mars. So whereas light thrust will land you on the Moon, you can float down to Venus's surface (which is terrible once you get there), and a combination of thrust, chutes, and maybe bouncing will land you on Mars, Mercury requires a lot of thrust, period. Putting all of that rocket fuel into the payload that has to get to Mercury, the delta-v problem becomes even starker. And then there's the heat. The ESA lander would have landed near the north pole to escape some of the *ground* heat, but the sun is just as bright anywhere it appears in the Mercurian sky (except that seasonally, it is considerably less glaring at aphelion).

Another way to deal with the heat problem would be to land at night and wait for sunrise, dying sometime thereafter. That has the disadvantage of preventing descent imaging. It would be particularly sad to have the thing die when the sun had come up enough to burn the craft but before the landscape had been illuminated!

I don't think anyone would expect the panorama to be anything but a novel notion for wallpaper for your monitor -- there is no reason to suspect the hermean regolith to differ structurally from lunar regolith. We would almost certainly see a landscape like one of the Apollo landscapes, give or take a modest difference in hue. From earth-based remote sensing we already know that Mercury's surface is much lower in Fe than the Moon's; Messenger will tell us more about the raw composition. Overall, I'd say Mercury's surface is more burning with heat than burning with questions that a lander can answer.

I think the first mission to Mercury's surface ought to be a combination of Deep Impact and Stardust: a low-flying flyby craft in solar orbit would skim the Mercurian dayside (at 90,0 or 270,0) at aphelion, while an impactor flying just ahead would pound into the surface, blasting some regolith briefly up into a plume, which the flyby craft, trailing behind, would collect, and bring back on its Earth-intersecting orbit. We would obtain shattered fragments of Mercury that would, nonetheless, tell us the isotopic composition of Mercury's crust (which should be sufficiently pulverized already by impacts that smashing a sample once more is no great crime). The great value of THAT observation, aside from telling us about the early solar nebula and Mercury's evolution, is that it might permit the eventual identification of meteorites that originated on Mercury. We probably have, or will have, Mercury meteorites in collections -- identifying them as such would be a huge boost, because actually obtaining a non-fragment Mercury sample return would be a matter of enormous cost.

[Guest_BruceMoomaw_*]

(1) That Mercury smash-and-grab mission is a real idea -- in fact (although I know virtually nothing about it), there was apprently at one point a Discovery proposal to do just that for one of Mercury's polar regions (to also try and obtain information on the polar deposit composition).

(2) Actually, it is thought likely that Mercury's regolith differs somehat in closeup appearance from the Moon's simply because meteoroids have been smashing into it at much higher speed. At a mnimum, there should be a lot more melted impact glass mixed into it. It's questionable, however, whether any such differences would be interesting enough to be worth a camera. But:

(3) A Mercury lander WOULD have a lot more uses. We very badly need to know more about the planet's strange internal structure -- for which seismometers, magnetometers, and (if possible) heat flow probes would be invaluable. In fact, just plain old measurements of the planet's libration rate by tracking a lander would be very informative about its interior -- Stanton Peale once suggested a Mercury lander that would do nothing else whatsoever!

And while we might be able to get good data on the element makeup of Mercury's crust from a smash-and-grab mission, there are also some important mineralogy measurements (Raman, Mossbauer, X-ray diffractometry) that could probably be done neitehr by such a mission nor by an orbiter. Finally, a surface lander might tell us more about the planet's super-rarified atmosphere than we could discover from an orbiter.

[DDAVIS]

[quote=BruceMoomaw,Aug 16 2005, 07:53 PM]

(2) Actually, it is thought likely that Mercury's regolith differs somehat in closeup appearance from the Moon's simply because meteoroids have been smashing into it at much higher speed. At a mnimum, there should be a lot more melted impact glass mixed into it. It's questionable, however, whether any such differences would be interesting enough to be worth a camera.

I cannot imagine sending a lander to a planetary body without a camera! It would be interesting to see if the character of the surface varies from the Moon, and if there is a lot more impact glass than the lunar surface one would expect a more pronounced heliogenshein effect than what one sees on the Moon. The higher gravity might cause slightly different crater details on the small scale.

Don Davis

[djellison]

Well quite - of the planets on which one COULD land - it is only Mercury and Pluto from which we dont have surface imagery

Doug

[Guest_BruceMoomaw_*]

You're forgetting 2003 UB313, Doug... (Or, alternatively, The Planet That Must Not Be Named. Come to think of it, I hope the Potter craze hasn't gone so far that they end up naming the thing Voldemort.)

[um3k]

You're forgetting 2003 UB313, Doug... (Or, alternatively, The Planet That Must Not Be Named.  Come to think of it, I hope the Potter craze hasn't gone so far that they end up naming the thing Voldemort.)

I would much prefer Dumbledore.

[Guest_Richard Trigaux_*]

JRehling,
your smash and grab idea is interesting. It could be perhaps beterred if the impactor hits the surface with a very low angle, nearby horizontal, so that the plume would be also nearby horizontal. And the main spacecraft would travel right in at low relative velocity, we could perhaps even collect more than dust, little stones.



BruceMoomaw,
just to get the exact movement of Mercury from a lander would require only little electronics for that lander, just retro rocket and guidance devices, and avoiding heat by landing at night. The payload itself would be just a mirror, similar to the ones placed on the Moon, so that it could easily withstand heat and need no electronics, insulators and the like.

A still simpler method, although more speculative, would be to send special reflecting glass balls, protected into a kind of low melting point metal or plastic, and shot this on the ground without retrobraking. With a low enough impact velocity, the casings protects the glass balls. (An additionnal idea would be to fly the glass balls just behind a larger impactor, so that the plume would brake them). Once the sun rises, the casings melt, lefting the glass balls naked, so that they could be used for measuring distance with a laser shot. Not all glass balls would work, but if we send many a fair amount could work. This is not worse than landing the MERs into an airbag!




The idea of a lander on Mercury or Venus arises special concerns, due to the extreme heat. Maybe I shall start a thread about the suitable technos for this.