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.

Re:Venus is the hottest planet

[LordKronos]

Yes, that was the same thing I thought when I read it. I went to look it up because I thought maybe I had remembered incorrectly. According to wikipedia, Mercury has a max tempurature of 700K, while Venus has a mean of 737 K

Re:Venus is the hottest planet

[Anonymous Coward]

Mercury also has no atmosphere, so I don't think Messenger was going 12 times the speed of sound

I suppose you also think that when it's dark nothing can go the speed of light.

Re:Venus is the hottest planet

[viperidaenz]

I suppose you think sound travels the same speed regardless of the medium and temperature.

Re:Venus is the hottest planet

[Anonymous Coward]

It seems pretty clear they are using the speed of sound from the surface of the Earth under normal conditions. For areas near Mercury though, given the typical temperature of the solar wind, it would have a speed of sound ~100 km/s, some 20-30 times faster than the probe (and slower the solar wind itself which is hypersonic). Although right at the surface and especially on the dark side, Mercury has a very tenuous atmosphere which would be much colder than the solar wind temperature.

Re:Venus is the hottest planet

[Anonymous Coward]

I suppose you think outside an earth-based point-of-reference and would prefer if the rest of us stopped using similes and metaphoric terms to describe things to people who will never actually leave earth and have no other basis for comparison.

Re:Venus is the hottest planet

[davester666]

Chick's are generally hotter than dude's. At least for me.

Re:Venus is the hottest planet

[cyn1c77]

I suppose you think outside an earth-based point-of-reference and would prefer if the rest of us stopped using similes and metaphoric terms to describe things to people who will never actually leave earth and have no other basis for comparison.

People who don't have the ability to think quantitatively and rely purely on metaphor for all reasoning wouldn't even understand the concept of the speed of sound. They probably wouldn't also read space articles. So why cater to them?

Re: Venus is the hottest planet

[oobayly]

Rely? I know people who would have read that article (on a site like the BBC), but don't know what the speed of sound is. They would however know it's somewhere between a commercial aircraft's speed and a fighter plane. So "10 times the speed of sound" is better than "3400 m/s".

Saying that, using the speed of sound can annoy me because if it's a high altitude thing, is it 10 times the local speed of sound or STP speed - at -40 there a 10% difference.

Re:Venus is the hottest planet

[meta-monkey]

Only because all their greenhouses fled here.

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?

[LordKronos]

I assume it would take a lot of fuel for it to break orbit, but even so...what is to be gained by doing so vs just leaving it there as long as possible to collect whatever data it can until the bitter end?

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?

[Anonymous Coward]

The middle reason

Re:Why?

[amRadioHed]

What do you mean by deorbiting? It sounds to me like it was able to successfully deorbit.

Re:Why?

[amorsen]

Deorbit is what happened... If you mean actually escape from Mercury gravity, that would have shortened the mission due to the need to save fuel for a last burn. What would be the point?

Re:Why?

[Anonymous Coward]

What else could they do with it?

To land it would require at least 4GJ of energy to slow a 513kg craft from 14,000kph down to 0. For what? To land a space craft with no fuel? That's hundreds of kilograms of hydrazine.

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?

[Tablizer]

The sun's gravitational attraction caused the orbit to decay...

I'm not sure "decay" is the best choice of words. It grows from a (somewhat) round orbit to an elliptical orbit over time due to an effect I forgot the name of. The momentum is the same, it's just that if that momentum is translated into enough of an elliptical orbit, the probe happens to bump into the planet.

If the planet was a point source of gravity, say Mercury was converted into a black hole, then I believe the probe's orbit would cycle between round and elliptical over time due to that damned effect I forgot the name of and can't find an Google.

Re:Why?

[Diac]

Lol just to clarify I was curious why it hit the planet when it ran out of fuel instead of having some extra rockets or extra tank to send it away from hitting mercury as it could have hit something of scientific interest on the planet. I wondered if it was like when they rammed the LCROSS satellite/probe into the moon to study the impact results was this something similar or was it simply that it just ran out of fuel and fell......Hard into mercury.

Hmmm who gets to name the new crater btw lol

Re:Why?

[Anonymous Coward]

They simply squeezed every drop of science they could from the probe, and then let go of it. The final orbital maneuvers were actually done with zero fuel left, by venting gas that had previously been used to pressurize the fuel tanks! That kept it in orbit for another month, and allowed a few more low-altitude observations. Probes like this never carry enough fuel to reach escape velocity, there's just no particular reason for it to leave orbit and the capability would come at the cost of less scientific payload. Once it orbits a planet (at low altitude), it's guaranteed to eventually impact it because maintaining the orbit requires small corrections on a regular basis.

Re:Why?

[Irate Engineer]

Maybe this needs clarification - the probe was not "deorbited" i.e. deliberately smashed into Mercury in a controlled manner. They did all they could to keep it up in orbit as long as possible, but the fuel finally ran out and its orbit inevitably decayed and it finally impacted today.

The sun influenced the orbit significantly, and the idea of a 2-body perpetually stable orbit wasn't close to the actual situation. Maintaining orbit required a lot of active control.

Even in Earth orbit, the ISS needs a periodic re-boost because its orbit is affected by the very thin atmosphere at its altitude, as well as attraction by the moon.

Re: Why?

[Anonymous Coward]

It wasn't designed for that. Everything it gathered was digital and already sent back to us. It worked 3 years longer than planned, but it has no way of launching back to us. The launcher did not go with it.
TL;DR because it's too expensive to make it any more than a 1 way trip.

Re:Why?

[Anonymous Coward]

Which part of "why not save some before it ran out" didn't you understand?

Re:Why?

[Tablizer]

Let me rework that last paragraph:

If the planet were a point source of gravity, for example say Mercury was converted into a black hole, then I believe the probe's orbit would gradually cycle between round and elliptical over time due to that damned effect I forgot the name of and can't find on Google.

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]

And to what end? It's not like it harms anything. It's just another crater on the planet.

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

But like you said, not like it harms anything.

Re:Why?

[Anonymous Coward]

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

If it can survive the trip to Mercury, four years in orbit and then a crash landing then fair play to it.

Re:Why?

[Irate Engineer]

Because that would have been a waste of fuel. Getting to another planet for scientific observations, even back up to Venus or Earth, was not energetically possible. The best use of the fuel was to keep it in orbit around Mercury where it could collect the most data, which it did, and some.

Mercury is pretty deep down in the Sun's gravity well. It took a lot of fuel to get down there, and climbing out would take nearly as much. It was a one-way trip from the get-go. This is not a tragedy. It was a damned good use of money for science. Great "bang for the buck".

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?

[Irate Engineer]

The momentum was not constant, as the gravitational force of the sun acted on the probe. F = d/dt(mv). The momentum decreased, lowering the orbit.

Re:Why?

[Irate Engineer]

Too bad this was posted AC, but this needs to get modded to the moon.

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?

[Anonymous Coward]

I'm sure the periodic 3rd body perturbation effects (gravitational effects are conservative) on eccentricity were far greater than any nonconservative effects from solar radiation pressure. Increase the eccentricity with constant angular momentum and the periapsis moves in. Basically what the other guy was saying. With a 60 mile periapsis, it doesn't take much to make the orbit go ballistic.

Re:Why?

[Anonymous Coward]

There were already good answers in sibling posts (e.g. LordKronos, amorsen).
The mystery is that MAXOMENOS got to +5 informative without answering the question, while posts that did stayed at +2.

Re:Why?

[viperidaenz]

It would have been cooler to escape from Mercury. It would then hurtle towards the sun. All it would take is an extra 1500kph... That's like... probably all the fuel they had left once they got in to orbit.

Re:Why?

[viperidaenz]

Don't forget the impact with the surface at 14,000kph. That's equivalent to a bit less than a ton of TNT.

Re:Why?

[Anonymous Coward]

It used up over two thirds of its fuel to get into orbit around Mercury. The flight path it took to get there was extremely fuel conservative too, so even as is, the project did a lot with very little fuel budget. In order to save itself, it would have had to be in a very different orbital inclination or much larger orbit, both of which would have defeated the primary goals of the project. Once it entered into the orbit it had, it had not enough to fuel to make such radical changes, just enough to maintain it as is.

Re:Why?

[camperdave]

Blast it away from Mercury for what purpose? What else are you going to study out there? Mercury doesn't have any moons. There's nothing Sunward, and not enough thrust do climb away from the Sun to anywhere else - even if you could break out of Mercury's gravitational pull. The instruments were purpose built to study the surface of Mercury, so they're not going to register anything meaningful if you do break out of orbit.

So I ask you, why blast away from Mercury? What are you going to accomplish?

Re:Why?

[camperdave]

Save it for what? So it could spend three or four years STUDYING NOTHING before running out of fuel?

Re:Why?

[camperdave]

Maybe this needs clarification - the probe was not "deorbited" i.e. deliberately smashed into Mercury in a controlled manner. They did all they could to keep it up in orbit as long as possible, but the fuel finally ran out and its orbit inevitably decayed and it finally impacted today.

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.

That, to me, is the really sad part. They should have reserved enough fuel to deliberately crash it so that the impact could be seen and analyzed.

Re:Why?

[Anonymous Coward]

Obligatory xkcd

The title of the person in charge of sterilisation is the Planetary Protection Officer

Re:Why?

[AK Marc]

It takes less than that. If you want to escape Mercury, you'd need to go Mercury's escape velocity parallel to the orbit, or greater if headed away from the sun, and less if headed towards the sun. So to burn up in the sun would be less than the stated or free-body calculated Mercury escape velocity. Also, the number is reduced because the calculated number is related to from a rest at the surface, not for something already moving in orbit. It wouldn't take nearly that much more velocity to end up orbiting the sun, or smashing into it, if you were already moving and in orbit.

Re:Why?

[blue trane]

Don't they have a lot of solar energy to work with, to move away from the Sun?

Re:Why?

[dbIII]

Greg Egan did a pretty good book about a civilization living in orbit around a black hole - "Incandesance". Keeping pen and writing paper handy while the characters are working out their local laws of motion is recommended. The first "we're not in Kansas anymore" moment is when the concept of two different directions for up depending on where the character is standing becomes apparent.

Re:Why?

[floppycat]

due to that damned effect I forgot the name of and can't find an Google.

Kozai mechanism?

Re:Why?

[Anonymous Coward]

All the ac's here had a meeting and we forgive you for the idiotic comment.

Re:Why?

[Anonymous Coward]

This my little one is where we "accidentally" genocided the Mercuriums,

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?

[Talderas]

In order to generate propulsion, spacecraft need to eject material. In rocket engines they use combustion to blow a super-hot gas out the back. On probes they may use something less extreme and literally eject gas from a tank. In either case you have a finite amount of fuel to use to generate propulsion and once that fuel runs out you cannot generate more propulsion.

Collecting solar energy to convert into electricity doesn't help. You're not collecting something that you can eject so no propulsion. You would need to find a way to take electricity to generate delta-v.

Re:Why?

[Talderas]

The kaboom was on Mercury, but it wasn't Earth-shattering.

Re:Why?

[danbert8]

The "crashing shit into the moon to study seismic waves" science required seismic sensors that were installed by the Apollo astronauts. Mercury has none of these such sensors. There isn't anything to collect or send data from on Mercury.

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:Why?

[DaChesserCat]

Save it for what?

To try to bring it home to Earth? Where we have no means to recover it and bring back to the the surface? Even if we did, to put it in some museum, so elementary school kids on a field trip can look at it and go "whatever?" After it's been exposed to years of hard radiation in space, closer to the Sun?

Seriously. Save it for what? Better to let it finish it's job and become its own monument. Maybe, someday, another probe will get to see it. We sure as hell won't.

Re:Why?

[Anonymous Coward]

Don't worry, you are not alone, I was thinking the same thing. Glad you replied like you did lol.

I guess some people can't comprehend threads and keep context in mind for more than a post or two back. I see it a lot and it drives me nucking futs!

Re:Why?

[radja]

in theory you could use a solar sail, this does not require the ejection of material. I don't think a solar sail is powerful enough though, but I'm not a rocket scientist. I just play one in KSP.

Re:Why?

[Tablizer]

That's it! I kept searching with words like "...effect", "...phenomenon", "...principle", etc. "Mechanism" I couldn't remember.

Thanks Much!

Re:Why?

[camperdave]

The same thing they do with other impactors - a flash of light. Then they can do a spectral analysis from which they derive the chemical composition.

Re:Why?

[Aristos Mazer]

I think you miss the point of the question. AC wants to know why we just bombarded a planet with our debris -- scarring another world rather than take the extra fuel to clean up our mess and avoid adding to the craters on Mercury. This is a sentiment I've heard elsewhere -- that the extra science time wasn't worth the environmental cost of dumping our stuff on Mercury.

AC: What you miss is that Mercury is a lifeless rock already marked by tons of craters. One more makes little difference. There wasn't any benefit from the view of anyone working on the project in avoiding impacting Mercury. If this were Mars or someplace that humans might one day live, that would be different.

Re:Why?

[blue trane]

Hey, it was Purge day.

Re:Why?

[Anonymous Coward]

Then they can do a spectral analysis from which they derive the chemical composition.

Spectral analysis + years of arguing over the exact composition of the craft, as has happened with analysis of previous impact flashes.

Re:Why?

[blue trane]

I just saw this article on today's front page:

http://science.slashdot.org/st...

The EM drive is controversial in that it appears to violate conventional physics and the law of conservation of momentum; the engine, invented by British scientist Roger Sawyer, converts electric power to thrust without the need for any propellant by bouncing microwaves within a closed container. So, with no expulsion of propellant, thereâ(TM)s nothing to balance the change in the spacecraftâ(TM)s momentum during acceleration.

stable orbit

[Anonymous Coward]

So entering a stable orbit is not as easy as Captain Kirk makes it out to be?

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.

Re:stable orbit

[suutar]

Nope. Sulu did all the work, after all (of course, he still made it look easy :)

Re: stable orbit

[Anonymous Coward]

Seems like they were always worrying about the orbit decaying too.

Re:stable orbit

[Anonymous Coward]

It is "standard orbit" not stable, they never needed an orbit that would last 4 years.

Re:stable orbit

[david_thornley]

When did Kirk ever get the Enterprise into a stable orbit? They kept putting it in some sort of standard orbit, which would decay, threatening to smash the starship into the surface, every time it was relevant to the plot.

12 times the what?

[Anonymous Coward]

Speed of sound in what medium?

Re:12 times the what?

[WillgasM]

A vacuum, of course.

Re:12 times the what?

[Irate Engineer]

Space is not a perfect vacuum: http://en.wikipedia.org/wiki/Bow_shocks_in_astrophysics

Re:12 times the what?

[Anonymous Coward]

and temperature and pressure

Re:12 times the what?

[perryizgr8]

So does this mean that if I scream loud enough in space, someone can hear me?

Re:12 times the what?

[Talderas]

Well, you wouldn't scream as much as the gases in your lungs would rush out of your body. If you could somehow scream during that then one person would hear you scream but that person isn't in much of a position to help you.

Terrorism?

[Anonymous Coward]

The local inhabitants are going to be pissed...they'll call this a terrorist drone strike.

Yes Venus is the Hottest, BUT

[Laserfuzz]

How did a "news for nerds" poster fuck that up? I work in a planetarium, so I get asked this question daily.

Re:Yes Venus is the Hottest, BUT

[tomhath]

Mary Ann was the hottest, although some liked Ginger.

Re:Yes Venus is the Hottest, BUT

[Whiteox]

I would go with Ginger, but I'd be thinking of Mary Ann.....

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?

Re:Terrible news

[pushing-robot]

I felt a great disturbance in the force, as if millions of transistors suddenly cried out in terror...

Re:Terrible news

[Irate Engineer]

There were no survivors, as there were no passengers (unless one of those dope baggage handlers fell asleep in the cargo hold again).

Re:Terrible news

[blue trane]

Bacteria? Don't they keep finding it on Mars craft and such?

How long before Mercury retaliates?

[Anonymous Coward]

I would assume the inhabitants of Mercury will consider this a unprovoked attack and are right now preparing a retaliatory strike against Earth.

our Drone crashes into Mercury

[turkeydance]

hey! it's a Drone, ok? It Shouldn't Include Shiites (ISIS) would understand.

The speed of sound?

[ubergeek65536]

It's strange that the speed of sound on Mercury is the same as on Earth.

Re:The speed of sound?

[pushing-robot]

Don't worry, at least the speed of light is different.

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.

Re:Energy of the collision

[dskoll]

Gah! /. should let you edit comments. s/crated/crater/ of course.

Re:Energy of the collision

[Anonymous Coward]

Click, backspace, r. Must less typing.

ignore this space

[SternisheFan]

Posting to undo a mis-mod.

Re:ignore this space

[Anonymous Coward]

ffffffffffag

I thought...

[dohzer]

I thought I heard something.

Why not send it into the sun?

[Anonymous Coward]

What could two or so extra months orbiting Mercury tell us that 4 years hadn't already?

I mean, it survived pretty well up to this point, why not escape Mercury with whatever fuel was remaining before the last adjustment, and let the Sun's gravity take over? See how close it can get before burning up, study the radio waves radiating from it etc.

Re:Why not send it into the sun?

[Blaskowicz]

I have not done calculations, but there is conventional wisdom that it is very hard to get to the Sun, you need a lot of delta-v to get that orbital change. Assuming a lot of propeller left, you would likely get slightly closer to the Sun and get stuck there, then tiny push from the radiation pressure would slowly make you recede outwards.

Re:Welfare program ends in explosion.

[blue trane]

They should have shipped the Kansas state government up there to monitor the whole thing, make sure the computers weren't lazing around in the sunshine.

Poorly Written Submission

[Anonymous Coward]

There are several elementary errors of fact and in writing technique in this submission. I'm surprised slashdot accepted it.

1. Mercury is not the hottest planet. Venus is.

2. Speed of sound? Don't use comparisons with the speed of sound when you're writing a story about space. It just leads to debate about the speed of sound in different mediums. And btw, it's not "quicker," "faster" is the proper term in this context.

3. A crater the size of a tennis court? Where does it say this in the original linked BBC article? Sources please. Don't add something to a story that is not supported by the linked article. If the tennis court fact comes from another article, then link to it.

This poorly written submission is another excellent example that it is best to stick with what the original sourced article says. Don't try to embelish the facts, "put it in your own words," or add to the submission with your personal store of 9th grade science class knowledge. You just end up looking ignorant.

Why not crash into visible side?

[wired_parrot]

Would it not have been possible to have controlled the impact into the visible side of Mercury? I am assuming being able to witness the impact itself, and getting close-up photos of Mercury as Messenger was coming down, might have been valuable science to obtain.

Re:Why not crash into visible side?

[Anonymous Coward]

This.

I'm sure there are good reasons, but it's a shame they couldn't treat it as a very brief 'lander' and grab snapshots of the surface before impact.

Next Mission

[wardrich86]

NASA to send new space probe "Skype" in to fill its place.

Mission scientists confirmed...

[swooshxx]

"Mission scientists confirmed the impact minutes later, when the craft's next possible communication pass was silent."

That's not much of a confirmation. Need they be reminded of V'ger?

Lithobraking

[cmdr_klarg]

I will admit to seeing the term "lithobraking" for the first time. Gave me a good chuckle. :)