6 ms·

> Scientists [were] worried that when [Cassini] loses power, it could crash into a pristine moon, contaminating a place where we might someday search for life

by luckyt 9y ago

> Scientists [were] worried that when [Cassini] loses power, it could crash into a pristine moon, contaminating a place where we might someday search for life Why is this so bad? Moons are pretty big compared to spacecraft, why are they so worried about the environmental damage of a single spacecraft weighing a few tons?

dottrap 9y ago
They are worried Earth microbes on the satellite might eventually be confused for life on the moon.
pavel_lishin 9y ago
Think fifty years in the future. The Herschel probe lands on Enceladus, armed with instruments that can sample the water and test it for presence of biological life. A hit! A world-changing discovery, we've detected DNA! ...but wait, hang on a second, check the records. Isn't this really close to where we predict that Cassini crash-landed after it ran out of fuel and contact was lost in 2023? Shit. Shit shit shit. We have no idea whether this DNA is actually from the oceans of Enceladus, or if it's from a hardy bacteria that hitched a ride on Cassini all the way from Earth, and thrived in the oceans of Enceladus. If it's thriving in Enceladus, it might be out-competing the life that's already there. We may never know, we can't know what native Enceladus life was like, or if it even existed! They're not worried about knocking down some space-trees; they're worried about it being impossible to assess scientific results with accuracy.
- nsxwolf 9y ago
  Shouldn't we expect life on Enceladus to be different enough to tell the difference?
  - sosuke 9y ago
    I'd say when we can ensure no contamination there isn't any reason not to ensure no contamination. What if it turned out that the DNA found was similar to ours? Now think of the difference in chances if we'd dropped Cassini on the surface or if we hadn't.
  - pavel_lishin 9y ago
    > Shouldn't we expect life on Enceladus to be different enough to tell the difference? We should likely have as few expectations as possible. The discovery of an entirely different form of life on Enceladus would be as incredible as the discovery that life on Enceladus uses the same DNA building blocks as we do.
- ekianjo 9y ago
  > We may never know, we can't know what native Enceladus life was like, or if it even existed! To be fair we don't even know if life on Earth is native to it in the first place or not...
  - Cthulhu_ 9y ago
    True, in fact I think a dominant theory is that life came from Somewhere Else, hitching a ride on an asteroid. Another one is that it formed around the volcanic vents in the ocean.
    - Retric 9y ago
      Solar wind makes live seeding from outside the solar system significantly less likely. It's possible, but considered far less likely than you might think. On the other hand life going from Earth to Mars/other moons etc is expected.
  - adrianN 9y ago
    Finding life on Saturn's moons that looks eerily related to life on Earth would provide some weight to panspermia theories. But only if we could be sure that we didn't bring it there ourselves.
- FuNe 9y ago
  Why not worrying about the same thing about Saturn though? The best thing would be to slingshot Cassini in outer space like Voyagers but I guess they wouldn't have this option here.
  - crispyambulance 9y ago
    The moons of Saturn are small even compared to the earth. One could expect far more "wreckage" to survive the entry to a moon. Getting into Saturn, however, is vastly different. Casssini has broken up into many smallish, white-hot pieces only to eventually merge into clouds of ammonia at -200C that are blowing at extreme velocities. Further down, there are clouds of water at 0C and then metallic liquid hydrogen. Perhaps pieces could end up there or on the rocky core? Saturn is a weird place. How much worse than an autoclave is entry to Saturn?
    - Pigo 9y ago
      Titan is actually larger than Mercury. Just something I learned yesterday while reading Cassini posts. It really puts the size of Saturn into perspective.
      - dmoy 9y ago
        Mercury is also real damn small. Just a tiny bit bigger than Earth's moon.
      - FreeFull 9y ago
        Titan is larger, but also significantly less dense. Mercury is more massive than Titan.
        craftyguy 9y ago
        Mercury is pretty much just a leftover iron core
  - delibes 9y ago
    Gas giants are a much less obvious place for native life to evolve, at least from our understanding of life. Enceladus appears to have liquid water, which makes it much more likely (still slim). That said, Arthur C Clarke included giant city-sized lifeforms floating in the clouds of Jupiter in his 2001, 2010, 2061 series. And Isaac Asimov wrote "Victory Unintentional" in the robots series.
- mcbits 9y ago
  It seems pretty unlikely that Earth life could accidentally seed any moon of Saturn, and extremely unlikely that it could out-compete life that's been adapting to that environment for eons. As in, even less likely than Earth's surface bacteria hitching a ride on probes down to volcanic vents on Earth and out-competing the life there. Maybe it would find a small niche to fill. No matter how careful we are, if we do find life on another planetary body, genetically similar enough to be confused with present-day Earth life, the assumption should be that it is from Earth and there had been no other life. Unfortunately it leaves "are we alone?" unanswered, but it answers "can life exist beyond Earth?"
  - ceejayoz 9y ago
    Cassini has an RTG, so a crash into something like Encaladus could potentially create a nice warm little oasis for Earth bacteria to live in. A few decades and some on the fringes of this oasis might adapt - there's believed to be liquid water there. Don't have to out-compete if there's nothing there, and being similar to Earth life wouldn't let us rule it out - rocks from asteroid impacts are known to have travelled between Earth and Mars, so it's not outrageous for one to have travelled between Earth and Saturn.
    - mcbits 9y ago
      If we find life on Enceladus that looks just like Earth life, the null hypothesis is that it came from Earth. That won't change, whether we crash a probe there or not. Finding extant life anywhere beyond Earth would still be a paradigm-shattering discovery, even if we must assume it arrived from Earth on a probe or ejecta. The probe we send to test for life must, of course, be completely sterile to ensure it's not detecting its own hitchhikers.
      - ceejayoz 9y ago
        > If we find life on Enceladus that looks just like Earth life, the null hypothesis is that it came from Earth. Sure, and ruling that out is easier if we can say for certain we didn't crash an old space probe nearby.
- Robotbeat 9y ago
  "no idea" and "impossible" is a stretch of the truth. Hyperbole. There are lots of tools in the biologist's shed for this sort of thing, and we know how to use them (think of all the field work done anywhere on Earth, such as Antarctica... if the task of sorting life was impossible, we should defund all of that immediately). We have an idea. It just makes it harder in the extremely remote chance that it crashes in such a way that it could contaminate an icy moon and have any passengers start growing wildly. Personally, I think that, fundamentally and cosmically, the whole point of Gaia producing a species which can send probes to other planets is contamination. We're Gaia's reproductive system.
MikeFez 9y ago
>contaminating a place where we might someday search for life Should it have crashed into a moon that we later find life on (especially should the life be remarkably similar to that here on earth), whose to say we didn't send it there via Cassini in the first place? Avoiding this problem entirely seems to be the best bet, also allowing them to collect atmospheric data from Saturn on the way out.
- pvaldes 9y ago
  In some cases we could still estimate a probable answer. Biologists can separate two cryptic species of living beings placed into an species complex, just taking a look to its DNA. The mutation rate among two isolated bacteria from earth and saturn would be noticeable. Unless we discover an active saturnian's nano-turism to pass the holidays on earth's oceans, the only reasonable answer to explain two identical or almost identical bacteria in both planets is a contamination event.
nickhalfasleep 9y ago
Cassini's mission profile was to do progressively more dangerous activities as the time allowed. Nearing propellant exhaustion, they investigated close to the rings and the planet's upper atmosphere before destruction. Contamination prevention was only a part of the decision.
celias 9y ago
"All solar systems missions are subject to constraints designed to minimize the unintentional impacts of Mars and, when applicable, the contamination of icy satellites such as Europa, Enceladus, and Ganymede." [1], also see [2] "The Huygens probe which landed on Titan was not sterilized as the chances of finding life were considered insignificant. From further investigations it is evident that chances for life on Titan are higher than initially thought. Although forward contamination in this case is still considered unlikely, it reinforces the need to ensure we protect extra-terrestrial chances of life." [3], also see the second page of [4] [1] https://planetaryprotection.nasa.gov/requirements https://planetaryprotection.nasa.gov/requirements [2] https://saturn-archive.jpl.nasa.gov/faq/FAQHuygens/ https://saturn-archive.jpl.nasa.gov/faq/FAQHuygens/ [3] http://www.spacesafetymagazine.com/space-exploration/extraterrestrial-life/cassini-huygens-preventing-biological-contamination/ http://www.spacesafetymagazine.com/space-exploration/extrate... [4] http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens/No_bugs_please_this_is_a_clean_planet http://www.esa.int/Our_Activities/Space_Science/Cassini-Huyg...

by luckyt 9y ago

dottrap 9y ago

They are worried Earth microbes on the satellite might eventually be confused for life on the moon.

pavel_lishin 9y ago

Think fifty years in the future. The Herschel probe lands on Enceladus, armed with instruments that can sample the water and test it for presence of biological life. A hit! A world-changing discovery, we've detected DNA! ...but wait, hang on a second, check the records. Isn't this really close to where we predict that Cassini crash-landed after it ran out of fuel and contact was lost in 2023? Shit. Shit shit shit. We have no idea whether this DNA is actually from the oceans of Enceladus, or if it's from a hardy bacteria that hitched a ride on Cassini all the way from Earth, and thrived in the oceans of Enceladus. If it's thriving in Enceladus, it might be out-competing the life that's already there. We may never know, we can't know what native Enceladus life was like, or if it even existed! They're not worried about knocking down some space-trees; they're worried about it being impossible to assess scientific results with accuracy.

nsxwolf 9y ago
Shouldn't we expect life on Enceladus to be different enough to tell the difference?
- sosuke 9y ago
  I'd say when we can ensure no contamination there isn't any reason not to ensure no contamination. What if it turned out that the DNA found was similar to ours? Now think of the difference in chances if we'd dropped Cassini on the surface or if we hadn't.
- pavel_lishin 9y ago
  > Shouldn't we expect life on Enceladus to be different enough to tell the difference? We should likely have as few expectations as possible. The discovery of an entirely different form of life on Enceladus would be as incredible as the discovery that life on Enceladus uses the same DNA building blocks as we do.
ekianjo 9y ago
> We may never know, we can't know what native Enceladus life was like, or if it even existed! To be fair we don't even know if life on Earth is native to it in the first place or not...
- Cthulhu_ 9y ago
  True, in fact I think a dominant theory is that life came from Somewhere Else, hitching a ride on an asteroid. Another one is that it formed around the volcanic vents in the ocean.
  - Retric 9y ago
    Solar wind makes live seeding from outside the solar system significantly less likely. It's possible, but considered far less likely than you might think. On the other hand life going from Earth to Mars/other moons etc is expected.
- adrianN 9y ago
  Finding life on Saturn's moons that looks eerily related to life on Earth would provide some weight to panspermia theories. But only if we could be sure that we didn't bring it there ourselves.
FuNe 9y ago
Why not worrying about the same thing about Saturn though? The best thing would be to slingshot Cassini in outer space like Voyagers but I guess they wouldn't have this option here.
- crispyambulance 9y ago
  The moons of Saturn are small even compared to the earth. One could expect far more "wreckage" to survive the entry to a moon. Getting into Saturn, however, is vastly different. Casssini has broken up into many smallish, white-hot pieces only to eventually merge into clouds of ammonia at -200C that are blowing at extreme velocities. Further down, there are clouds of water at 0C and then metallic liquid hydrogen. Perhaps pieces could end up there or on the rocky core? Saturn is a weird place. How much worse than an autoclave is entry to Saturn?
  - Pigo 9y ago
    Titan is actually larger than Mercury. Just something I learned yesterday while reading Cassini posts. It really puts the size of Saturn into perspective.
    - dmoy 9y ago
      Mercury is also real damn small. Just a tiny bit bigger than Earth's moon.
    - FreeFull 9y ago
      Titan is larger, but also significantly less dense. Mercury is more massive than Titan.
      - craftyguy 9y ago
        Mercury is pretty much just a leftover iron core
- delibes 9y ago
  Gas giants are a much less obvious place for native life to evolve, at least from our understanding of life. Enceladus appears to have liquid water, which makes it much more likely (still slim). That said, Arthur C Clarke included giant city-sized lifeforms floating in the clouds of Jupiter in his 2001, 2010, 2061 series. And Isaac Asimov wrote "Victory Unintentional" in the robots series.
mcbits 9y ago
It seems pretty unlikely that Earth life could accidentally seed any moon of Saturn, and extremely unlikely that it could out-compete life that's been adapting to that environment for eons. As in, even less likely than Earth's surface bacteria hitching a ride on probes down to volcanic vents on Earth and out-competing the life there. Maybe it would find a small niche to fill. No matter how careful we are, if we do find life on another planetary body, genetically similar enough to be confused with present-day Earth life, the assumption should be that it is from Earth and there had been no other life. Unfortunately it leaves "are we alone?" unanswered, but it answers "can life exist beyond Earth?"
- ceejayoz 9y ago
  Cassini has an RTG, so a crash into something like Encaladus could potentially create a nice warm little oasis for Earth bacteria to live in. A few decades and some on the fringes of this oasis might adapt - there's believed to be liquid water there. Don't have to out-compete if there's nothing there, and being similar to Earth life wouldn't let us rule it out - rocks from asteroid impacts are known to have travelled between Earth and Mars, so it's not outrageous for one to have travelled between Earth and Saturn.
  - mcbits 9y ago
    If we find life on Enceladus that looks just like Earth life, the null hypothesis is that it came from Earth. That won't change, whether we crash a probe there or not. Finding extant life anywhere beyond Earth would still be a paradigm-shattering discovery, even if we must assume it arrived from Earth on a probe or ejecta. The probe we send to test for life must, of course, be completely sterile to ensure it's not detecting its own hitchhikers.
    - ceejayoz 9y ago
      > If we find life on Enceladus that looks just like Earth life, the null hypothesis is that it came from Earth. Sure, and ruling that out is easier if we can say for certain we didn't crash an old space probe nearby.
Robotbeat 9y ago
"no idea" and "impossible" is a stretch of the truth. Hyperbole. There are lots of tools in the biologist's shed for this sort of thing, and we know how to use them (think of all the field work done anywhere on Earth, such as Antarctica... if the task of sorting life was impossible, we should defund all of that immediately). We have an idea. It just makes it harder in the extremely remote chance that it crashes in such a way that it could contaminate an icy moon and have any passengers start growing wildly. Personally, I think that, fundamentally and cosmically, the whole point of Gaia producing a species which can send probes to other planets is contamination. We're Gaia's reproductive system.

MikeFez 9y ago

>contaminating a place where we might someday search for life Should it have crashed into a moon that we later find life on (especially should the life be remarkably similar to that here on earth), whose to say we didn't send it there via Cassini in the first place? Avoiding this problem entirely seems to be the best bet, also allowing them to collect atmospheric data from Saturn on the way out.

pvaldes 9y ago
In some cases we could still estimate a probable answer. Biologists can separate two cryptic species of living beings placed into an species complex, just taking a look to its DNA. The mutation rate among two isolated bacteria from earth and saturn would be noticeable. Unless we discover an active saturnian's nano-turism to pass the holidays on earth's oceans, the only reasonable answer to explain two identical or almost identical bacteria in both planets is a contamination event.

nickhalfasleep 9y ago

Cassini's mission profile was to do progressively more dangerous activities as the time allowed. Nearing propellant exhaustion, they investigated close to the rings and the planet's upper atmosphere before destruction. Contamination prevention was only a part of the decision.

celias 9y ago

"All solar systems missions are subject to constraints designed to minimize the unintentional impacts of Mars and, when applicable, the contamination of icy satellites such as Europa, Enceladus, and Ganymede." [1], also see [2] "The Huygens probe which landed on Titan was not sterilized as the chances of finding life were considered insignificant. From further investigations it is evident that chances for life on Titan are higher than initially thought. Although forward contamination in this case is still considered unlikely, it reinforces the need to ensure we protect extra-terrestrial chances of life." [3], also see the second page of [4] [1] https://planetaryprotection.nasa.gov/requirements https://planetaryprotection.nasa.gov/requirements [2] https://saturn-archive.jpl.nasa.gov/faq/FAQHuygens/ https://saturn-archive.jpl.nasa.gov/faq/FAQHuygens/ [3] http://www.spacesafetymagazine.com/space-exploration/extraterrestrial-life/cassini-huygens-preventing-biological-contamination/ http://www.spacesafetymagazine.com/space-exploration/extrate... [4] http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens/No_bugs_please_this_is_a_clean_planet http://www.esa.int/Our_Activities/Space_Science/Cassini-Huyg...