Messenger's Mercury Trip Ends With a Bang, and Silence

mpicpp writes with an expected followup: Nasa's Messenger mission to Mercury has reached its explosive conclusion, after 10 years in space and four in orbit. Now fully out of fuel, the spacecraft smashed into a region near Mercury's north pole, out of sight from Earth, at about 20:00 GMT on Thursday. Mission scientists confirmed the impact minutes later, when the craft's next possible communication pass was silent. Messenger reached Mercury in 2011 and far exceeded its primary mission plan of one year in orbit. That mission ended with an inevitable collision: Messenger slammed into our Solar System's hottest planet at 8,750mph (14,000km/h) — 12 times quicker than the speed of sound. The impact will have completely obliterated this history-making craft. And it only happened because Mercury has no thick atmosphere to burn up incoming objects — the same reason its surface is so pock-marked by impact craters. According to calculations, the 513kg, three-metre craft will have blasted a brand new crater the size of a tennis court. But that lasting monument is far too small to be visible from Earth.

Comments

Venus is the hottest planet

[Anonymous Coward]

greenhouse effect

Re:Venus is the hottest planet

[EmeraldBot]

greenhouse effect

AC's right, as rare as that happens. If you compare the average temperatures of Venus with those of Mercury, Venus is indeed the hotter planet.

Why?

[Diac]

Why did they smash messenger into mercury? Was it because they had no choice as there was not enough fuel to deorbit? If so why not save some before it ran out and blast it away from mercury. Or was there a scientific reason? Like the next probe could analyze the impact crater and compare it to ancient ones to see what the difference will be.

Or did they do it simply because it was cool?

Re:Why?

[Irate Engineer]

The sun's gravitational attraction caused the orbit to decay. It ran out of maneuvering fuel and could not raise its orbit anymore. This was expected - the mission fulfilled all of its primary objectives and some. A lot of good science was had from that probe.

Re:Why?

[MAXOMENOS]

There wasn't enough fuel to sustain orbit. The team responsible for this went to heroic lengths to keep it in orbit --- including at one point venting the spacecraft's helium to give it a final boost. This was all done so the probe could keep sending back data, which it did happily. In the end we got approximately four times the expected data we wanted from the probe.

Not bad for government contractors.

Re:Why?

[EmeraldBot]

Why did they smash messenger into mercury? Was it because they had no choice as there was not enough fuel to deorbit? If so why not save some before it ran out and blast it away from mercury. Or was there a scientific reason? Like the next probe could analyze the impact crater and compare it to ancient ones to see what the difference will be.

Or did they do it simply because it was cool?

I'm guessing because they would have needed to use extra fuel for that, and that would have been less time to study the planet. Given the time and costs of getting there, I can't blame them for wanting to squeeze out that extra bit of time. Plus, it will be pretty neat if humans ever do make it back there - it'll be a landmark to those of the future, what we in the past could accomplish.

Re:Why?

[Dutch Gun]

The question is sort of answered in the article if you read between the lines:

Despite being able to look back with pride, Dr Raines said this was still a sad day for Messenger scientists.

"Pretty much all the instruments are still doing great, so that makes it a little harder," he told BBC News. But the mission was always going to be limited by the fuel needed to maintain its difficult orbit.

"To be honest, I've seen this day coming for a long time and it's just one of these things that I've not been looking forward to. I'm really going to be sad to see it go."

So, the fuel was needed to keep the orbit stable, and without that, it degraded and impacted the planet. It's likely they didn't have enough fuel to even break away from orbit, and if they did, it would have shortened the mission duration. And to what end? It's not like it harms anything. It's just another crater on the planet.

Re:Why?

[Irate Engineer]

This *was* the bitter end. It used up all of its fuel. It had to periodically lift its orbit ever since it arrived in 2011. It finally just ran out of fuel. It has been in orbit around Mercury for nearly four years (initially planned to survive only one year, due to the intense solar radiation).

Re:Why?

[LordKronos]

Yes, I know this was the bitter end. That was kind of my point. The person I replied to asked why they didn't just have it break orbit and "blast it away from mercury". I was saying, even if they could have done so (which I'm not sure they ever could have), how would that have been better than what they actually did (ie: leave it there to the bitter end)

Re:Why?

[Anonymous Coward]

"Save it" how, exactly? If it only had enough fuel to maintain orbit for four years then it didn't have enough to bring it back to Earth (which wasn't part of the mission anyway, so then what?). Increasing the orbit would lessen the value of the data and it still would have decayed again eventually.

They got three more years of data out of by using up the fuel keeping it in orbit. "Saving" the physical structure of the probe by breaking orbit would have been a much bigger waste and deprived them of all of that data. The data is worth much much more than the stupid probe itself.

Re:Why?

[Irate Engineer]

Umm, that "microbial life we 'forgot'" (which we didn't) has been baking in the UV glow of the sun, unoccluded by clouds or atmosphere of any kind, for well over 4 years. And it crashed into a planet that been baking in the UV glow of the sun, unoccluded by clouds or atmosphere of any kind, for well over 4 billion years, as well. If the bugs survived, they earned it.

Re:Why?

[Dutch Gun]

Until the microbial life we 'forgot' about infects and destroys another local biome (or creates one in the first place)

Who's "we"? Certainly not NASA.

Anything expecting to make contact with another celestial body undergoes sterilization for exactly this reason, which should take care of most organisms. And of course, it would need to survive the trip and eventual impact, as well as then miraculously be adaptable to Mercury's incredibly hostile climate. In this particular case, the probability of native contamination is deemed so low that only a level I (lowest of five levels) decontamination procedure is needed.

Re:Why?

[LordKronos]

What the hell? You keep replying to me in a manner as if you are countering my point, when you are saying the exact same thing I am saying. Are you NOT comprehending what I am posting? Diac asked why they didn't save some of it's fuel to have it leave mercury. My post was saying, even if they could do that, there's nothing to be gained by having it leave mercury...it's better to have it spend it's time and fuel remaining at mercury as long as it can, gathering as much data as it can.

Before you reply to me again, please read the entire chain of posts, back to Diac's original post.

Re:Why?

[danbert8]

Seen by who? If you can't get a good look at the crater it made now, then what did you expect to see at the time of impact?

Re:stable orbit

[Irate Engineer]

About as easy as Captain Kirk entering a stable relationship with the blue skinned hottie he picks up while in that orbit.

Terrible news

[squiggleslash]

I think like everyone on Slashdot my heart extends to the families of the passengers who died as the ship hit Mercury. I assume there were no survivors?

Energy of the collision

[dskoll]

14000 km/h = 3889 m/s, so a 513kg craft crashing at that speed into a planet would need to dissipate 0.5 * 513 * 3889 * 3889 = 3.8 GJ of energy, or just under a ton of TNT. So yeah... the crated would probably be fairly impressive from close up.