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NASA Space

Messenger's Mercury Trip Ends With a Bang, and Silence 108

Posted by timothy from the hell-of-a-way-to-go dept.
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.
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Messenger's Mercury Trip Ends With a Bang, and Silence More

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

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  • Venus is the hottest planet (Score:5, Informative)

    by Anonymous Coward on Thursday April 30, 2015 @05:58PM (#49589699)

    greenhouse effect

    • Re:Venus is the hottest planet (Score:5, Informative)

      by EmeraldBot ( 3513925 ) on Thursday April 30, 2015 @06:03PM (#49589729)

      greenhouse effect

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

    • 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

    • Only because all their greenhouses fled here [xkcd.com].

  • Why? (Score:2)

    by Diac ( 1515711 )

    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? (Score:5, Informative)

      by Irate Engineer ( 2814313 ) on Thursday April 30, 2015 @06:07PM (#49589765)
      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: (Score:1)

        by Tablizer ( 95088 )

        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 bet

        • Re: (Score:2)

          by Tablizer ( 95088 )

          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: (Score:2)

            by dbIII ( 701233 )
            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.
        • 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.

    • 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? (Score:5, Informative)

        by Irate Engineer ( 2814313 ) on Thursday April 30, 2015 @06:15PM (#49589839)
        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).

        • 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)

          • 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 [wikipedia.org]. 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

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

              • 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 woul

                • Re: (Score:2)

                  by radja ( 58949 )

                  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.

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

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

                  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 accel

            • 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 a

    • Re:Why? (Score:5, Informative)

      by MAXOMENOS ( 9802 ) <mike&mikesmithfororegon,com> on Thursday April 30, 2015 @06:07PM (#49589775) Homepage

      There wasn't enough fuel to sustain orbit [cbsnews.com]. 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.

    • 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.

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

    • Re: (Score:2)

      by amorsen ( 7485 )

      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?

      • 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: (Score:2)

          by AK Marc ( 707885 )
          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 orbit

    • Re:Why? (Score:5, Informative)

      by Dutch Gun ( 899105 ) on Thursday April 30, 2015 @06:14PM (#49589831)

      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: (Score:1)

      by Diac ( 1515711 )

      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

      • 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.

    • 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 perio

      • 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.

    • 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?

  • stable orbit (Score:1)

    by Anonymous Coward

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

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

    • Re: (Score:2)

      by suutar ( 1860506 )

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

    • 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? (Score:1)

    by Anonymous Coward

    Speed of sound in what medium?

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

  • Comment removed (Score:5, Funny)

    by account_deleted ( 4530225 ) on Thursday April 30, 2015 @06:34PM (#49589973)
    Comment removed based on user account deletion
  • hey! it's a Drone, ok? It Shouldn't Include Shiites (ISIS) would understand.

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

  • Energy of the collision (Score:5, Interesting)

    by dskoll ( 99328 ) on Thursday April 30, 2015 @07:32PM (#49590335) Homepage

    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.

  • Comment removed based on user account deletion

  • I thought I heard something.

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

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

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