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Landing on Mercury on equator at perihelion
Rem31
post Mar 21 2006, 12:18 AM
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How will it be to make a manned landing at Mercury at its closest to the sun (perihelion) on its equator when the sun is in the zenith ,what are the dangers of a landing then? Do we need to be protected against the sunheat and radiation then? How strong is the heat and radiation of the sun then ,and is it dangerous when the solaractivity is high then? What kind of spacesuits do we need then? Better protected suits than we have used on the apollo moonlandings i think. Can you explain how a landing on Mercury will be when it is at perihelion and land on its equator with the sun directly overhead? I hope it will ever happen. Lets start discuss about it.
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antoniseb
post Mar 21 2006, 12:25 AM
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QUOTE (Rem31 @ Mar 20 2006, 07:18 PM) *
How will it be to make a manned landing at Mercury


It sounds like you want the manned spaceflight forum.
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RNeuhaus
post Mar 21 2006, 02:25 AM
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QUOTE (Rem31 @ Mar 20 2006, 07:18 PM) *
How will it be to make a manned landing at Mercury at its closest to the sun (perihelion) on its equator when the sun is in the zenith ,what are the dangers of a landing then? Do we need to be protected against the sunheat and radiation then? How strong is the heat and radiation of the sun then ,and is it dangerous when the solaractivity is high then? What kind of spacesuits do we need then? Better protected suits than we have used on the apollo moonlandings i think. Can you explain how a landing on Mercury will be when it is at perihelion and land on its equator with the sun directly overhead? I hope it will ever happen. Lets start discuss about it.

Up to now, there is no plan to land on Mercury but just to orbit around on the poles by the year 2011 . So the spacecraft must catch up the speed starting from 29.8 km/sec (relative to Sun) when it leaves the Earth and arrives at Mercury at 47.9 km/sec after one Earth Fly-by, 2 Venus Fly-By, and 3 Mercury Fly-By by March 18, 2011. Long trip!

If you want to be closer to Mercury, start visiting at the following URL: http://messenger.jhuapl.edu/the_mission/index.html

Nobody is thinking in exploring on Mercury. It is out of our present paradigma. The next time would be on Moon close to the year 2020 and maybe to Mars close to the year 2030.

Rodolfo
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Rem31
post Mar 21 2006, 03:42 AM
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But how will a (hypothetical) manned landing on Mercury be at its perihelion on the equator with the sun in zenith? Can you give an idea of how that looks like ,like i have written in the beginning of this thread? And i really dont understand why we dont put a lander or rovers like on mars on Mercury. We have landed a lander on Venus,Mars,but why not on Mercury? I and a lot of people on earth are waiting for the moment that a lander is on its way to Mercury and that is going to land on this planet to send the first images of the surface of Mercury back to earth ,like the venera,s did on Venus and the vikings and pathfinder did on Mars. The only thing i can say is that we forgot 1 planet ,And that is Mercury. Thanks.
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Guest_BruceMoomaw_*
post Mar 21 2006, 04:25 AM
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A manned landing on Mercury at perihelion -- or an unmanned one, for that matter -- would be difficult as Hell (which may be appropriate). The problem wouldn't be as severe as that on a Venus lander, but it would be plenty hard -- you would not only need to have an extremely efficient reflecting shield to fend off the heat radiation from the Sun, but also another to deal with that being reflected and emitted from Mercury's surface. (This, in fact, is one reason why the Messenger orbiter will be put into a highly elliptical orbit around Mercury: to give it time to cool off again from each of its low-altitude periapses over Mercury's surface.) As for the design of any EVA walking suit that could cope with that heat: I shudder even to think about the problem. The high-energy particle radiation and X rays from the Sun at that range would also pose a very difficult problem for any manned mission that close to the Sun -- we'll have enough danger from those during long-duration manned trips to Mars and near-Earth asteroids.

However, temperature-wise, there are plenty of other places that either an unmanned or manned lander could touch down on Mercury that would be a cinch. Its near-polar regions are quite tolerably cool -- which is why it has ice as its poles -- and its nightside very quickly cools down after sunset, stays cold, and even stays within modest temperature ranges for a short time after sunrise again.

A polar or nightside landing on Mercury is entirely feasible with the technology we have right now. The trouble, as usual, is simply money. Europe's BepiColombo, which consists of a large and low-altitude European orbiter and a small secondary Japanese one for magnetospheric studies, was originally also supposed to include a very small lander to touch down within about 3 degrees of the pole -- but, since Mercury is an airless world with a gravity field considerably stronger than the Moon's (and therefore requiring a larger mass of braking fuel), in the end the cost and mass of the lander was just too much for ESA's already-strained budget to endure and they cut it out of the mission. At some point it certainly will be done by someone; Mercury's surface almost certainly looks almost indistinguishable from the Moon's, but there are a great many interesting geophysical and compositional instruments they could land there on even a single lander. But that's likely to be a couple of decades off (at least), just for monetary reasons.
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Guest_Richard Trigaux_*
post Mar 21 2006, 06:09 AM
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QUOTE (Rem31 @ Mar 21 2006, 01:18 AM) *
How will it be to make a manned landing at Mercury at its closest to the sun (perihelion) on its equator when the sun is in the zenith ,what are the dangers of a landing then? Do we need to be protected against the sunheat and radiation then? How strong is the heat and radiation of the sun then ,and is it dangerous when the solaractivity is high then? What kind of spacesuits do we need then? Better protected suits than we have used on the apollo moonlandings i think. Can you explain how a landing on Mercury will be when it is at perihelion and land on its equator with the sun directly overhead? I hope it will ever happen. Lets start discuss about it.


If you want to have an idea of what Mercury looks like, lit a good fire into your chimney. Set yourself at the right distance where heat is pleasant. This is like Earth. Now divide the distance by three and look what happens. It is Mercury.

On Mercury at midday, not only the Sum burns like the opening of a furnace, but the ground itself is nearby red hot.
Fortunately the nights are long and they would allow for a lander to work and do interesting job. But it would have no solar energy. From where the projects to land near the poles.
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edstrick
post Mar 21 2006, 08:49 AM
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Exploring Mercury is difficult. While it's relatively easy to use a single Venus flyby to fly a spacecraft past Mercury, it passes the planet at high speed. Such high speed that it would take an enormous propulsion system to simply get into orbit around the planet. The Mercury Messenger orbiter mission does multiple Mercury flyby's to reduce the spacecraft's aphelion and make it possible to get into orbit with a "reasonable" sized rocket system. And it will take many years to get there.

Landing on Mercury is harder. You are orbiting a planet with a deeper gravity well than the moon, and with no atmosphere to reduce speed from orbital velocity. You have to do it ALL with rockets. Bigger rockets than needed to land on the Moon.

When you get there, you will find an impact generated regolith, made of basaltic to anorthositic (we think) rock, very similar -- indeed visually identical -- to lunar highlands plains and cratered terrain sites.

If Mariner 10 had found a truely exotic planet, as un earth-like or un moon-like than Venus or Titan, we'd have a much greater interest in exploring the planet. Certainly, Mercury has been neglected, as has Venus in many ways. But for good reason, I'm afraid.
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Guest_Richard Trigaux_*
post Mar 21 2006, 09:08 AM
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At least, and orbiter with high resolution mapping and imaging, and IR spectrum analysis, perhaps radar probing, would be fine. We know little about Mercury and we may find unexpected/unexplained things. And the big mystery is why Mercury has no volcanoes. As far as we know. Another thing would be to detect dust storms (from static electricity, as believed on the Moon) or Transcient "Lunar" Events.

After, a lander would have to check isotopes ratios and place a seismometre, so that we have an idea of Mercury inner structure. After?
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edstrick
post Mar 21 2006, 10:26 AM
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Robert Strom (I think) and subsequent researchers have pretty clearly shown that Mariner 10 images show some volcanic flows and deposits. Their geologic morphology is poorly preserved due to considerable primary and secondary impact cratering, and many of the features were observed at such high sun angle that morphology is poorly if at all visible. What they do see is some crater and inter-crater plains with flow fronts and ponded morphology that is rather unlike basin ejecta deposits that fooled Apollo era geologists into thinking Apollo 16 was going to explore highland volcanism. They also see color boundaries in high sun angle data that look like flows with different color and thus chemistry from adjacent plains and crater deposits.

Everything seems to be pretty seriously old. Relatively young volcanics like on the Moon seem to be absent or very scarce, and "constructional" volcanic features are scarce or absent.

One long recognised factor is that the entire crust has scattered lobate escarpments, apparently compressional thrust faults that indicate the crust has been under compression during most of the visible geologic record. This makes it much harder for magma to find a route to the surface as all the channels and fissures are squeesed tightly shut, as compared with a crust under extension.
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Guest_Richard Trigaux_*
post Mar 21 2006, 11:06 AM
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hey, that is interesting, and fairly different of the Moon. Maybe Mercury has a completelly different history. Worth sending a visible light mapper and IR spectrometre.

The compression of Mercury crust (and perhaps mantle too) is often explained as the result of the cooling and contraction of its huge iron core. This contraction would have created all the compression faults (perhaps following the Mare Caloris impact). The Mare caloris itself produced considerable destructions, for instance at the antipodes all the mountains were thrown into the air by the shockwave.
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Guest_Richard Trigaux_*
post Mar 21 2006, 11:18 AM
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An interesting job too for a probe would be sensing Mercury's gravitation field. For this it requires a trajectory coming from afar and going as close as possible from the ground. For this, the probe would perform a very close passage, perhaps some kilometres, which would place it on a very elliptic orbit.

From this orbit, it could make a global map of Mercury.
After, the orbit would be circularized at lowered, so that the probe could make high resolution views.
Ideally, on an airless world, the orbit could be lowered at will, theoretically some kilometres, lower than an airliner. But from a previous discution on a lunar orbiter, it appeared that, due to the presence of mascons on the Moon, such orbit is not stable and it ends up crashing on the ground. A similar problem may exist on Mercury, limiting the lowest altitude.

An interesting prediction, from the crust compression model, is that it could exist many underground tectonic cavities. If there is yet any form of volcanism or outgassing, it would take place here, and the cavities may have a complete atmosphere (with a pressure gradient and all). Eventually this could lead to some outgassing at very low pressure, if there are exit points.
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ljk4-1
post Mar 21 2006, 03:20 PM
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Come on, guys - just land at night!

How about landing on the terminator (where the temperature is balanced,
right?) and having the mission follow just ahead of sunrise. The planet takes
59 days to rotate, so it should be slow enough for the explorers.

I saw them do this on the Chronicles of Riddick, so it must be true.


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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JRehling
post Mar 21 2006, 05:37 PM
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To summarize what other posters have written: Mercury is the hardest place in the solar system to land.

It takes more delta-v to get from the Earth to Mercury than to any other planet. Including Pluto. In fact, a minimum-energy voyage to Alpha Centauri would cost less delta-v than a minimum-energy voyage to Mercury! (Of course, the former would take millions of years.)

Among the solid bodies in the solar system, Mercury is unique in terms of having a pretty high escape velocity (roughly a tie with Mars for third-highest, behind Earth and Venus) but NO atmosphere to assist in the deceleration from cruise to landing. So it requires the most hardware to undertake a soft-landing of any solid body in the solar system! That's two categories in which Mercury is THE hardest!

Those two difficulties combine: You have to take all of that soft-landing hardware to Mercury, which means that the launch will involve a very large rocket for a given payload.

The other difficulty, thermal, makes Mercury more difficult than almost anywhere else: Venus is worse in this respect, but only because Mercury has cooler poles and night. Landing on the equator in daytime would make Mercury very hard in that respect too. We don't have any hardware that could survive those surface conditions unless it involved a nuclear-powered refrigerator, and now we've tripled the (not just additive but multiplicative) mass problem.

Takeoff from Mercury would be as difficult as from Mars, and then the cruise back to Earth would be VERY hard: again, the biggest delta-v leap of any planet for a back-to-Earth trajectory.

All told, I'm not sure if anything less than a Saturn V could launch a Mercury equivalent of a MER, assuming that we could build a rover that could survive Mercurian conditions. It's safe to say that the Mercury equivalent of Apollo would involve technology far beyond anything yet developed. Imaginable, perhaps, but not yet developed. And the long cruise to Mercury would mean that a solar storm would have an excellent chance of killing the crew. If you utilize gravity assists from Venus, the cruise gets longer.

It's got sort of a joke-like difficulty to it. I'll predict that by the time we had the rocketry to perform a Mercury human mission, the state of robotics would make any such mission purposeless. But I won't live long enough to collect on that bet.
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Guest_BruceMoomaw_*
post Mar 21 2006, 09:42 PM
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Even Arthur C. Clarke, the Keeper of the Holy of Holies, said in "Odyssey Three" that, at a time when humans were routinely poking around comets and the like, only two manned landings had ever been made on Mercury -- and neither of them got much attention. The place has certainly got plenty of interest for geologists, but as Ed said it just isn't distinctive enough to have any pizzazz for people not intensely interested in science.
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JRehling
post Mar 21 2006, 10:02 PM
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QUOTE (BruceMoomaw @ Mar 20 2006, 08:25 PM) *
A polar or nightside landing on Mercury is entirely feasible with the technology we have right now.
[...]
At some point it certainly will be done by someone; Mercury's surface almost certainly looks almost indistinguishable from the Moon's, but there are a great many interesting geophysical and compositional instruments they could land there on even a single lander. But that's likely to be a couple of decades off (at least), just for monetary reasons.


A good bang-for-the-buck mission might avoid a high-latitude constraint by making a night landing and carrying a strobe light for imaging the vicinity. Because the surface will not cool immediately after sundown, it would be best not to land in daytime just before sunset. To allow a mission plenty of duration for seismic (or, alternately, lifetime for a rover), it could land about 10-20% of the way into local night, study the vicinity for about 45 days (night on Mercury is 54 Earth days), and then get a sunrise panorama of the background before sunlight cooks the craft.

Another approach would come from the unique fact that the Sun shows retrograde motion on Mercury because the revolution at perihelion overtakes the rate of rotation. A carefully-targeted lander could alight somewhere that was in night, then experienced a very brief "day" of a sunrise-then-sunset. So long as the engineering team could set the lander down precisely, the length of that day could be arbitrarily brief, and a rotatable "parasol" could mean that the craft would take no direct solar heating while the ground would experience only trivial heating in the short run. A lander aimed at just the right longitude could thus experience a short sol (for imaging) and go on to run other studies during a few more Earth days of nighttime before a longer sol cooked the craft.

And of course, there is the polar option. Conceivably, a lander could be sent into an area of eternal night, and never face a thermal constraint at all (except during cruise), but such a landing site would be idosyncratic (and therefore interesting, but differently interesting than just a generic Mercury landing site).
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