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A couple of comments on the question In the Outer Solar System, on which planets/moons could any man-made object ever land? suggesting that there is no scientific benefit to a crash on a moon, reminded me of the recent LADEE intentional crash. It seems like there may have been at least half a dozen, intentionally crashed for scientific rationale.

How many space craft have been intentionally crashed through 2014 (include pending/planned)?

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LADEE is actually an exception! It was crashed on the far side of the Moon, so the crash was not observed and had no scientific purpose. Phantastically, I think, is the claim that it was done in order to make sure it wouldn't crash into a historic Apollo site, as if there would be any probabilty for that. Cassini will end its mission by crashing into Jupiter in order to not risk contaminating any of the icy moons. That too lacks scientific purpose. LCross and Grail are other Lunar crashed spacecrafts since 2009. –  LocalFluff Apr 23 at 11:09
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Cassini will crash into Saturn, of course. I was thinking about Galileo which has crashed into Jupiter. –  LocalFluff Apr 23 at 11:15
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Let's not count those crashing into Earth's atmosphere, otherwise the number is huge... –  PearsonArtPhoto Apr 23 at 13:41

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up vote 6 down vote accepted

The vast majority of these have been around the moon. Here's a list of what I can find (Using Wikipedia):

  • Luna- 2 (Spacecraft and rocket)
  • Ranger- 4, 6, 7, 8, 9
  • Apollo LEMs- Apollo 12, 14, 15, 17.
  • Apollo S-IVB- Apollo 13, 14, 15, 16, 17
  • 1990's missions- Hiten, Lunar Prospector
  • 2000's missions- SMART-1, Moon Impacting Probe, Chang'e 1, Chandrayaan-1, SELENE, LCROSS shepherding spacecraft, LCROSS Centaur,

Okay, on to the planets/comets/ etc!

  • Scott and Amundsen- (Mars Impactors for the Deep Space 2 mission)
  • Deep Impact- impacted a comet
  • Galileo Probe - "Impacted" Jupiter, although there isn't really a Jupiter surface
  • Galileo- After the end of it's mission, "impacted" Jupiter.

By my count, that's 25 Lunar Impacting missions, and 5 others, for a total of 30.

So, what reasons do they do intentional crashes? Here's some of the most common reasons.

  1. Most of the Apollo crashes were to assist in determining the composition of the moon. The Astronauts left seismometers on the moon, which the exact landing spot and time of an intentional crash allowed them to figure out the composition of the moon.
  2. Some crashed to create plumes, and figure out what was in them. Most of the later lunar probes (LCROSS, SMART-1, etc) have done this, plus the Deep Impact space probe. Some of these were an afterthought, as a mission was ending they wanted to get some value out of it, others were done as a primary mission.
  3. Some use the impact of the crash to try and get scientific instruments on the ground. These include MIP, and the Deep Space 2 missions.
  4. Some are done to prevent contamination. This includes the Galileo crash, as Cassini will also follow.
  5. Luna-2 was actually crashed as a propaganda strike, littering the surface with Soviet ribbons.
  6. The Ranger missions were designed to see the moon up close, for a very short period of time. They ended with impact of the Moon.

Some lunar missions (Quite a few) ended in less controlled manners. There is a finite lifetime for a Lunar mission, of only a few weeks to months without fuel. Missions weren't listed that didn't crash at a pre-defined time and place. LADEE for one is included in this list.

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+1. Here's two more to add to your list: The Mars impactors Scott and Amundsen which together formed the Deep Space 2 mission. Apparently they impacted a bit more than expected. They didn't return any data. –  David Hammen Apr 23 at 15:40
    
I thought there was a Mars Impactor or two, I just couldn't find the data... Thanks! –  PearsonArtPhoto Apr 23 at 15:42

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