A Moon of Saturn Has a Sea, Scientists Say • Hacker News Board

Re: A Moon of Saturn Has a Sea, Scientists Say

#41

Post by Tuna-Fish » Fri, Apr 04, 2014, 2:39 AM UTC

hrjet wrote: post #39

didgeoridoo wrote: post #31

Earlier quoted context omitted.

An object coming in from a rendezvous with Saturn would be traveling at a ludicrous speed. You would probably vaporize on lunar impact. The Earth's atmosphere can help slow it down to a reasonable velocity--otherwise you have to carry a lot more fuel to burn in a slow-down maneuver.

Similar to how a swing-by is used to accelerate a space-vehicle, I wonder if a swing-by could be used to decelerate as well.

It can. The boost is proportional to the cos(final exit trajectory in relation to the planet, velocity of planet) -- so if the probe leaves the planet opposite to the direction it goes around the sun, it slows down.

(that is, the probe as whole can still orbit the sun in the same direction as the planet, it just needs to do it slower.

Re: A Moon of Saturn Has a Sea, Scientists Say

#42

Post by Tuna-Fish » Fri, Apr 04, 2014, 2:42 AM UTC

Hello71 wrote: post #20

civilian wrote: post #18

Earlier quoted context omitted.

Eh, I've played KSP, an orbital rendezvous in LEO on your return isn't that hard. If you have enough precision and fuel leftover to start a safe decent, you have enough precision and fuel to dock with the ISS. I'm surprised that we aren't equally worried about contaminating Enceladus with terran microbes.

psst, kerbal is not a substitute for actual physics.

However, it turns out we can introduce actual physics into kerbal. http://forum.kerbalspaceprogram.com/threads/68502-WIP-Princi... + real solar system + realism overhaul.

Re: A Moon of Saturn Has a Sea, Scientists Say

#43

Post by thaumasiotes » Fri, Apr 04, 2014, 6:51 AM UTC

danieltillett wrote: post #25

anigbrowl wrote: post #23

Earlier quoted context omitted.

Transpermia seems like a theory rather than a fact. While I think you're probably correct, it's better to be ultra-conservative on questions like this.

Of course it is only a theory, but a very plausible one given the frequency of rock transfer between planets and the toughness of microbes that allow them to survive in space for long time periods (both empirical facts). There is really no way of proving transpermia - even if we to travel to Enceladus and found microbial life there how would we ever prove how it got there.

> given the frequency of rock transfer between planets

What is this frequency, exactly? My impression was that all planets are constantly bombarded with rocks from space (not from other planets), but that it would be extremely surprising for a rock to e.g. leave Earth and end up on Mercury.

Re: A Moon of Saturn Has a Sea, Scientists Say

#44

Post by thaumasiotes » Fri, Apr 04, 2014, 6:59 AM UTC

megablast wrote: post #38

hellbanner wrote: post #11

"They found that the moon’s gravity was weaker at the south pole. At first glance, that is not so surprising; there is a depression at the pole, and lower mass means less gravity. But the depression is so large that the gravity should actually have been weaker." They found the gravity was weaker.. but it should actually have been weaker. So is it weaker or stronger?

Weakerer is not yet a word.

Similar idea:

In the board game Evo, your odds of success in combat are determined by comparing the number of horns your species has to the number the other species has.

Specifically, the following circumstances are considered:

- Each species has the same number of horns as the other

- One species has one more horn than the other

- One species has two or more more horns than the other

It's always fun to explain that part.

In the current context, "weakerer" isn't a word, but it would be quite normal to say "even weaker".

Re: A Moon of Saturn Has a Sea, Scientists Say

#45

Post by elnate » Fri, Apr 04, 2014, 7:23 AM UTC

jmpe wrote: post #2

"Dr. Tsou devised a way to capture comet particles and bring them back to Earth for NASA’s Stardust mission and has been suggesting a similar method for a spacecraft that would fly through Enceladus’ plumes and then return to Earth for scientists to examine. The challenges are to make sure that the interesting particles would not break apart, to take precautions that any alien life would not infect Earth, and to fit…

In regards to the contamination,

I don't think that would be a real risk. Earth life has spent billions of years both adapting and adapting to the environment to make it the best growing medium and even then it exists in exclusive bands. For example, put a polar bear in the desert or a fresh water fish in salt water. It is more likely that we would have to take extreme care not to kill any lifeforms we brought back than to worry about them killing us.

Re: A Moon of Saturn Has a Sea, Scientists Say

#46

Post by fit2rule » Fri, Apr 04, 2014, 7:52 AM UTC

anigbrowl wrote: post #23

danieltillett wrote: post #21

If there is an sea on Enceladus then there will already be microbial life there [0]. Microbes can survive for ages in space [1] and there are plenty of rocks moving from the earth and all of the other planets and moons of the solar system [0,2]. One of the more interesting stories about microbes in space is that some survived on the moon for almost three years inside a camera [3]. It is not 100% certain that the micr…

Transpermia seems like a theory rather than a fact. While I think you're probably correct, it's better to be ultra-conservative on questions like this.

The point of this story is to demonstrate facts that make transpermia less of a theory and more of a reality. We're not there yet - so don't throw the baby out with the bathwater here. We're absolutely going to go there to find life.

Re: A Moon of Saturn Has a Sea, Scientists Say

#47

Post by netcan » Fri, Apr 04, 2014, 8:48 AM UTC

The last paragraph is good writing.

The challenges are to make sure that the interesting particles would not break apart, to take precautions that any alien life would not infect Earth, and to fit it into the $500 million budget of one of NASA’s lower-cost planetary missions.

It frames it all beautifully. Engineering feats solving problems you don't quite understand. Sci fi potential. Budgetary drudgery.

Re: A Moon of Saturn Has a Sea, Scientists Say

#48

Post by jmpe » Fri, Apr 04, 2014, 9:17 AM UTC

elnate wrote: post #45

jmpe wrote: post #2

"Dr. Tsou devised a way to capture comet particles and bring them back to Earth for NASA’s Stardust mission and has been suggesting a similar method for a spacecraft that would fly through Enceladus’ plumes and then return to Earth for scientists to examine. The challenges are to make sure that the interesting particles would not break apart, to take precautions that any alien life would not infect Earth, and to fit…

In regards to the contamination, I don't think that would be a real risk. Earth life has spent billions of years both adapting and adapting to the environment to make it the best growing medium and even then it exists in exclusive bands. For example, put a polar bear in the desert or a fresh water fish in salt water. It is more likely that we would have to take extreme care not to kill any lifeforms we brought back t…

You're seriously underestimating this issue.

- rabbits/cane toads in Australia [0][1]

- Japanese knotweed [2]

- Tumbleweed (yep, not as native as Hollywood suggests) [3]

- Algae [4]

... and the list goes on and on, here's a top-100:

http://en.wikipedia.org/wiki/List_of_the_world%27s_100_worst...

[0] http://www.youtube.com/watch?v=pgPhn4tYxJQ

[1] http://en.wikipedia.org/wiki/Cane_toads_in_Australia

[2] http://www.environment-agency.gov.uk/homeandleisure/wildlife...

[3] http://en.wikipedia.org/wiki/Kali_tragus

[4] http://plants.ifas.ufl.edu/node/89

Re: A Moon of Saturn Has a Sea, Scientists Say

#49

Post by danieltillett » Fri, Apr 04, 2014, 9:29 AM UTC

thaumasiotes wrote: post #43

danieltillett wrote: post #25

Earlier quoted context omitted.

Of course it is only a theory, but a very plausible one given the frequency of rock transfer between planets and the toughness of microbes that allow them to survive in space for long time periods (both empirical facts). There is really no way of proving transpermia - even if we to travel to Enceladus and found microbial life there how would we ever prove how it got there.

> given the frequency of rock transfer between planets What is this frequency, exactly? My impression was that all planets are constantly bombarded with rocks from space (not from other planets), but that it would be extremely surprising for a rock to e.g. leave Earth and end up on Mercury.

Link 0 suggests that 150 kg of rock ends up on Mars every year from Earth. It is not too hard to find rocks from Mars here on Earth.

Re: A Moon of Saturn Has a Sea, Scientists Say

#50

Post by TeMPOraL » Fri, Apr 04, 2014, 9:29 AM UTC

elnate wrote: post #45

jmpe wrote: post #2

"Dr. Tsou devised a way to capture comet particles and bring them back to Earth for NASA’s Stardust mission and has been suggesting a similar method for a spacecraft that would fly through Enceladus’ plumes and then return to Earth for scientists to examine. The challenges are to make sure that the interesting particles would not break apart, to take precautions that any alien life would not infect Earth, and to fit…

In regards to the contamination, I don't think that would be a real risk. Earth life has spent billions of years both adapting and adapting to the environment to make it the best growing medium and even then it exists in exclusive bands. For example, put a polar bear in the desert or a fresh water fish in salt water. It is more likely that we would have to take extreme care not to kill any lifeforms we brought back t…

I don't think anyone is worried about space bears or space fish; but bacteria / viruses / other basic replicator forms have much bigger resistance to harsh environments.