I know of no probes that have been sent to Mercury. Seems like it might be worth checking out, at least a little bit. Also, since the Voyagers are still in contact amd out of the solar system, would it be possible to send a probe to the surface? Would we be able to receive any useful data from such long distance?
Mariner 10 has already been to Mercury (back in the 70’s no less).
As for Pluto remember it is WAY out there and some don’t even consider it a proper planet (I think its status us still a planet but I’ve read some suggestions that it be downgraded from a planet to…I don’t know what but not a planet).
Even so Nasa is planning the Pluto Kupier Express mission. Still on the drawing board it is proposed to rendezvous with Pluto in 2020. However, the mission has been halted as currently proposed so it’s anybody’s guess if it will ever happen. There are a lot of other interesting things closer by vying for scarce funding money.
The Voyagers will not come anywhere near Pluto on their way out of the solar system. Even if they did they don’t have any probes to send down to the surface. About the best we could hope for would be pictures and I don’t know if we could receive even those from the Voyagers at that distance. It is already very hard to ‘hear’ them given that they have fairly weak broadcasting equipment on board. Add to that that they are already beyond their designed lifespan and I think we should count ourselves lucky they worked as well as they did.
Well, let’s throw some numbers into the equation.
Distance to pluto: 3.7 billion miles (Give or take a few feet)
Escape velocity of Earth: 11.2 M/s
Good enough to start out with. Let’s first assume that the satelite we send up today travels no faster towards Pluto than the speed it left Earth. That’s 40,320 MPH, for about 91,000 hours. If it left today, it would get to Pluto sometime around November 2011. It’s not going to leave today though and by the time it gets to Pluto its technology will be outdated. Useful, but outdated.
And if you say “ok, let’s strap on more fuel before lift off” then you have to add more fuel just because you’re adding on fuel, because fuel has weight. Then we get to the question of how much weight can we strap on this thing to send it on its way fast?
Then comes the really big question: why are we doing this? I’m not saying Pluto isn’t important. Far from it. But really…it’s a huge ball of ice. Whoopee! Aren’t there better places we could be sending our probes? I say we bounce the probe off Pluto and throw it out into the Kuiper belt or the where we can really learn something interesting.
I am in full accordance Earthman. It is a desolate, and un-interesting wasteland. There are far better places for your species to investigate.
If you’re interested in the topic of exploring Mercury, there was a good article about it in Scientific American a couple of years ago. The article said that there are a lot of important questions to be answered there, and that the reasons that Mercury has been neglected for so long are that some people think it’s not a very interesting place (the article gives a number of important reasons to be interested in Mercury, though) and that it’s harder than you might think to get a spacecraft there because it has to overcome Earth’s orbital velocity to get that close to the Sun.
Nevertheless, a Mercury orbiter is planned. Here’s a link to a web page about it:
Astro, you fool! You know you are not authorized to make contact with the natives. Now return to your suspended animation chamber, immediately!
The Big Giant Head
Oh, please!:rolleyes:
Everone KNOWS that the aliens gave us all the data we need on Pluto… Sheesh! Why should we bother?
[sup]Sorry! I couldn’t resist![/sup]
Mercury is getting another probe (and had one in the past). Pluto is the only planet (or just one of manny TNO’s) that never had a probe. There is some reason to hurry up to get to Pluto. It’s atmosphere will soon clapse (~20 years) as it moves futher away from the sun and won’t come back for 200 years.
Pluto is hard to study because when we send a probe it will take sooooo long to get there that we can’t design a new probe based on what the 1st one sees unless we are willing to wait a min of 20 yrs between launches.
Another problem I forsee is in order to get a probe in orbit we have used aerobraking (passing through the upper atmosphere) to blead off speed. When we sent the mars global survayer we guesses as to how ‘thick’ the atmosphere was and could have lost the probe (it was thicker then estimated). We don’t even know if Pluto will have an atmosphere when we get there. The probe will either take shot of it as it passed on it’s way out or have to carry enough fuel to insert itself in orbit.
Nuclear fuel is now taboo (Voyager uses nuclear fuel - that’s why we can still communicate w/ it) Solar power is not going to be practical that far out.
IMHO, I think we should send a probe to Pluto. If not for simple human curiosity, then for the scientific benefit of examining the largest known Kuiper Belt object which may be indicative of the initial building blocks of the planets in the solar system. “An uninteresting wasteland” my foot. Anyway, the Planetary Society (Carl Sagan’s organization) is still pushing hard to get this mission going.
k2dave Note - Solar power is insufficient much past Mars, never mind Pluto. Galileo (Jupiter), Cassini (Saturn)…nuke fuel.
tarnik Both Voyagers are beyond the distance of Pluto. And one of them (V1?) went “up” out of the plane of the solar system after its encounter with Saturn’s moon Titan, IIRC. The Voyagers are still sending useful info about the outer reaches of the sun’s influence. More info from this website…
Anyway, most of NASA’s attention for exploration is now on Mars (search for life, potential future manned mission) and the asteroids/comets. Darn limited funding. 
By the way, the International Astronomical Union (which gets to name everything in astronomy) says Pluto is still a planet.
If you want to probe Pluto go to Disneyworld. You might get thrown out though. 
This is sort of the gist of a serious restriction on any feasible Pluto mission, coupled with the fact that it’s far away and small. The distance means that to get there in a reasonable time, the probe has to be going pretty fast when it gets there. Aerobraking has been far from standard (Galileo didn’t use it at Jupiter nor will Cassini at Saturn) and the prospect is worse than k2dave thinks: we already know there isn’t enough of a Plutonian (?) atmosphere to make this practical. I’d even guess that the approach speeds are sufficiently high to make the idea dodgy even if there was more of an atmosphere.
As k2dave says, one’s either looking at a flyby or carrying enough fuel to slow the probe down in order to achieve orbit. The latter is a penalty all round in such missions. At least with a gas giant like Jupiter or Saturn, the gravitational pull is sufficiently great as to help capture. Pluto’s pretty puny and so, not only are you travelling much faster to start with, you have to hit a much slower final speed.
Hence Pluto Express is just a flyby. And a fast flyby of a small body (or two) at that. The ethos is cut things down so you at least get there reasonably quickly to take a few snaps. In my personal opinion, it’s worth doing, though I recognise that at least part of this is the human urge to “complete the set.”
Incidentally, I don’t think that relative datedness of the technology by the time they start taking data is a problem with such missions. This is true of most big science and it’s just something specialists accept.