Several news reports this week referenced the spacecraft Cassini as having “crashed” into the planet Saturn. Saturn is composed of gas, so what exactly does this mean? What actually happened to Cassini?
Turned into a radioactive fireball. The speed it hit the atmosphere leaves no room for other results. Except for a poor angle and it skipped off and is now tumbling around the outer planets.
Even with a poor angle resulting in a skip, the most likely outcome is another orbit and then a plunge into the atmosphere. The only way it could get ejected is with some fluke interaction with one of the moons during it’s extra orbit.
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The atmospheric burn up was intentional. Cassini was out of fuel. The burn up was designed to ensure that nothing biological hitched a ride from Earth and possibly contaminate.
There’s too much scrap in Earth’s orbit. We don’t want to start doing the same to the other planets.
Cassini crashed into Saturn in a similar manner as Comet Shoemaker-Levy crashed into Jupiter, although far less spectacularly.
We did the same thing with the Galileo probe around Jupiter, and for the same reason: There’s a chance that Earthly life might be able to survive on Europa or Titan, and there’s a chance that both of those bodies already have life of their own. So to be absolutely sure, you crash the probe into the planet, so you can be sure that it never crashes into the moon.
When a satellite “crashes” into Earth, it starts breaking up and burning up as it enters the atmosphere. Very little survives to hit the ground. Even manned spacecraft need to come in at a carefully controlled angle. If it comes in at too steep an angle, it will hit the denser atmosphere at lower altitude before it slows down sufficiently, and it burns up.
Same thing with Cassini, except the speed is much greater, and the atmosphere is denser. It should have burnt up quite thoroughly.
I can’t wait to see its last recorded moments.
Thanks. As I suspected, “crash” is used figuratively in this case. It generally refers to to solids colliding with each other, such as a meteorite hitting the earth. On Saturn, there isn’t anything to crash into.
But that does lead to another question. If Cassini was made of some super solid that was able to withstand the force from entering and friction against Saturn’s atmosphere, would it basically oscillate a few times crossing Saturns’s center before settling right at its core?
I would have guessed at some point the pressure would force the material into it’s solid state … however, if the above citation is true, then Cassini would slow down very quickly and gradually sink towards the core … perhaps Cassini is buoyant enough to settle away from the exact center …
1.) Whether it takes a split second or several seconds for Cassini to shatter into a billion pieces seems to be splitting hairs. At the speed Cassini was traveling, it might as well have hit a brick wall.
2.) All planets in the solar system are formed from the same stuff, it is just that some of them became large enough to retain more of their volatiles. Saturn has plenty of iron, silicates, and all of the other solid elements found on Earth, Mars, etc., so at the bottom of all those clouds on Saturn is a lump of rock and metal several times the mass of the Earth.
There won’t be spectacular final photos. Cameras were turned off early to use the bandwidth for other science data.
It was weird watching the Nova episode on this and see people excited about Huygens landing (err, crashing) on Titan but worried about contamination from Cassini. No mention of extra sterilization procedures done on Huygens.
Saturn already has more scrap orbiting it than any other planet. In fact, there’s so much that we can see it from Earth with a small telescope. But you’re right, we don’t want to add more if we can easily avoid it.
All interplanetary probes are sterilized to some extent before launch. I think for landers they do so more than for orbiters. I know they were especially careful to do it for the Viking landers on Mars, since they didn’t want even a remote possibility of contamination of its experimental results.
There’s an official at NASA whose job is to keep probes from contaminating other planets. Currently the position is open, so you might want to apply to be Planetary Protection Officer.
The last photo was yesterdays’ Astronomy Picture of the Day:
Not particularly interesting photo, real dark.
Today’s photo of galaxy M-81 is more interesting.
Webster’s defines “crash” (intransitive verb) as:
1 a :to break or go to pieces with or as if with violence and noise
1 b :to fall, land, or hit with destructive force
So Cassini did really, literally crash into Saturn.
Landing on Titan, like Mars, was done for scientific reasons, but accidentally crashing Cassini into one of the moons, especially Enceladus, would have no scientific value, so why take the chance. Furthermore, liquid water does not exist on Titan, but Enceladushides a salt water ocean under its icy surface. It is thought that it is possible life evolved based on the chemistry around hydrothermal vents.
I was wondering about this, too, so I looked it up a few days ago. NASA/JPL has this on their FAQ page:
According to this article:
These “further investigations” of Titan largely consist of those conducted by the Huygens probe itself. Scientists were apparently very surprised to find large bodies of liquid ethane, methane, and propane present on the surface of Titan consisting of multiple lakes and seas. While life as we know it requires the presence of liquid water*, there could be some other form of life that somehow utilizes the liquid hydrocarbons present on Titan.
*As others have stated, liquid water is apparently present on Enceladus beneath its icy surface, so it actually has a greater chance of harboring alien life.
Note: I presumed that they took extra care with Huygens. My comment was directed at the Nova episode omitting this while going on about the dangers of contamination with Cassini. That was what was odd.