In 2017, we sent Cassini crashing into Saturn to avoid contamination

"The spacecraft will burn up and disintegrate like a meteor in the upper atmosphere of Saturn," Preston Dyches, of NASA's Jet Propulsion Laboratory (JPL), told Space.com via email. "This was determined to be the best way to ensure the safe disposal of the spacecraft, so that there would be no chance of future contamination of Enceladus by any hardy microbes that might have stowed away on board all these years."

Why was is not considered the same to that on a mission to the moon?

Tardigrades - often called water bears - are creatures under a millimetre long that can survive being heated to 150C and frozen to almost absolute zero.

They were travelling on an Israeli spacecraft that crash-landed on the moon in April.

And the co-founder of the organisation that put them there thinks they're almost definitely still alive.

and adds later

Even though the little moss piglets are likely to have survived the moon crash, it might not be great that they're there.

"What it means is the so-called 'pristine environment' of the moon has been broken," says Open University professor of planetary and space sciences Monica Grady.

When spacecraft leave Earth they are bound by the Outer Space Treaty not to contaminate their environment.

"I don't think anybody would have got permission to distribute dehydrated tardigrades over the surface of the moon. So it's not a good thing."

Is there some reason the Israelis decided to ignore the precedent? Or is it just not that important to protect the Moon from contamination anymore?

  • $\begingroup$ This is not the first time orgaisms were sent to the Moon. China deliberately sent plants on its Chang-e 4 spacecraft, and the Apollo missions may have had some microscopic hitchhikers as well. $\endgroup$ – Oscar Lanzi Aug 9 '19 at 22:19

The care which avoiding contamination space agencies take is generally proportional to the probability they assess of there being native life. Some of Saturn's moons are considered possible candidates for life, so Cassini was de-orbited. At this point, we are pretty sure that the Moon doesn't have life (no water, atmosphere, or significant magnetic field). As such, the precautions taken are much less rigorous.

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  • $\begingroup$ Its more due to the fact that theres 28 day extreme hot and cold cycles combined with constant radiation bombardment. There are worlds with no atmosphere which are more protected than the moon like Eclandeus. $\endgroup$ – Magic Octopus Urn Aug 12 '19 at 21:38

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