The mission to discover if Jupiter’s moons support life | Hacker News Reader

The mission to discover if Jupiter’s moons support life

theguardian.com

101 pointssandebert58 comments

> Every time the Galileo spacecraft drew near to Europa, one of Jupiter’s icy moons, readings from the magnetometer instrument indicated that something inside the moon was interfering with the mighty magnetic field generated by Jupiter.

Well, they __did__ warn us to "attempt no landing there".

Hehe...thats a blast from the past :-)

It's incredibly cold in the outer solar system right? So why is it that there is liquid water in these moons? Is it some sort of geothermal heating?

What's the most complex life which could conceivably exist in such a cold environment? Presumably there's very little sunlight penetrating through the ice to the liquid ocean.

Tidal heating [1]

[1] https://en.m.wikipedia.org/wiki/Tidal_heating

Interesting stuff! Made me find that even rogue planets (free floating without orbiting any star) might theoretically be warm enough to support oceans and life: https://en.wikipedia.org/wiki/Rogue_planet#Warmth

Could be either tidal or geothermal. It’s been conjectured that even Pluto could have liquid water inside.

The point is that generic small outer solar system bodies have liquid water, whereas the generic inner solar system body doesn’t. If you think liquid water is the most important requirement for life then most of the habitat in the universe is outside the frost line.

It’s totally plausible that simple life could form around geothermal vents on such a moon but harder to believe you could support a complex ecosystem enough to evolve intelligent life without sunlight.

At the high pressures in such an underground ocean I wouldn’t expect our proteins to work, you can kill bacteria with very high pressure. I suspect that proteins that evolved in that environment could work just fine. I can picture a creature from that kind of world drilling up to the surface somehow, but the low pressure would be deadly and in a system like Jupiter where Io ‘breeds’ radiation (vapor from volcanos gets ionized, gets accelerated, ionizes more vapor) the surface could be a dangerous place.

Such a creature though might have a leg up on starfaring as getting into orbit might be easier (never mind building a beanstalk) and rather than being tempted by boring destinations like Mars (smaller planet, smaller civilization) they might go straight to cutting up wet/carbonaceous asteroids to build large (100-1000x more habitable area than Earth) habitats and if they developed D-D fusion they might be quicker to see the advantages of a comet-hopping lifestyle.

One of the Main limiters with underwater intelligent life would be industrialization. How are you going to use a steam engine underwater? What do you burn to heat it? Given that geothermal vents would be the source of life for such a species - capping them for machinery would also be unwise.

Why would geothermal vents be a source of life after the species has evolved reproduction?

Source of energy and materials…

In the same way our sun is for us. Life on Earth wouldn't last very long if you plopped a Dyson sphere between it and the sun.

Any motion can be used to do work. If there are underwater currents, that power can be captured and used.

It's also awash with radiation from Jupiter. If there's life, it won't be as we know it :)

Water is really good at radiation shielding.

I've heard that if you swim into a nuclear reactor spent fuel containment pool, you will actually measure the least radiation somewhere in the middle of the pool, thanks to shielding from the universe.

Spent Fuel Pool

https://what-if.xkcd.com/29/

Nice, thank you!

The last lines are the best...

  But just to be sure, I got in touch with a friend of mine who works at a research reactor, and asked him what he thought would happen to you if you tried to swim in their radiation containment pool.

  “In our reactor?” He thought about it for a moment. “You’d die pretty quickly, before reaching the water, from gunshot wounds.”

I know someone who worked at a medical isotope reactor and there were no guns there, at least not in the reactor area. Security tends to be much much further outside ;)

After all, remember some things in a reactor don't react well to bulletsch.

Does Jupiter emit any noticeable radiation?

Yes.

https://solarsystem.nasa.gov/planets/jupiter/in-depth/

> Near the planet, the magnetic field traps swarms of charged particles and accelerates them to very high energies, creating intense radiation that bombards the innermost moons and can damage spacecraft.

So basically like our van Allen belts but supercharged.

Technically, the answer to GP's question would be no, because Jupiter doesn't emit the radiation, it just traps and accelerates the particles (mostly coming from solar wind) in its magnetic field...

A lot of the radiation is produced by a ‘breeding’ process where volcanos on Io emit vapor that gets ionized and then accelerated to make more radiation that ionizes more vapor.

Katherine de Kleer said "It's like Io is the massive polluter of the Jupiter system" on the Lex Fridman podcast #184, the Io part starts ~14mins in for the curious

Thanks!

Jupiter's radiation is so intense that Europa Clipper has a _super weird_ mission profile (a bunch of fly-bys instead of an orbit) so that the spacecraft doesn't spend too much time cooking in all that.

https://europa.nasa.gov/

The current Juno probe flies in 53 day orbits where only a few hours are in heavy radiation. It has made 48 orbits. The mission has been extended 7 years to 2025. If Juno runs low on fuel or the hardware breaks down, it will be crashed into Jupiter to avoid hitting and contaminating a moon.

The quick answer: Yes and from a human visitor perspective, lethally high amounts. It's the single most intense emitter of radiation in the solar system except for the sun itself. If we wanted to colonize any planet with plentiful moons, Saturn would be a much better candidate at least in this regard.

Also, though another reply here mentioned Jupiter not emitting its own radiation, this isn't quite correct. It does, almost like a small pulsar.

Europa is enticing because life would exist under a few km of ice, more than enough to prevent radiation from causing too much problems.

The hydrothermal vents, where the main sources of energy are hypothesized to be, would be deep enough.

From Earth's hydrothermal vents, we know sunlight isn't necessary for life although energy is.

We don’t know if life started in the light though and then migrated to the vents and adapted. My memory of it is that this is an unanswered question so far.

It's definitely an open question. But in his book "The Vital Question", Nick Lane makes an interesting case that they're actually the origin of all life: https://nick-lane.net/books/the-vital-question-why-is-life-t...

We know that life is older than photosynthesis. I'm not aware of another light-dependent metabolic process that could predate chemosynthesis.

Its a good hypothesis that life start at deep volcanic vents. Geologist Robert Hazen conducted lab experiments showing that all steps of the metabolic citric cycle occur in this environment without needing catalytic enzymes. Chemical reduction of magma provides the energy. As life developed enzymes to improve metabolism, it could migrate to colder, lower pressure environments.

Very cool! Does anyone know why we don't use Juice tools to also observe IO and the other moons of Jupiter in more detail/orbit.

Is it fuel constraints only?

It takes too long to go to these places. We need some sort of thrusters with which we can reach these places in months.

There's no getting around acceleration. Subjecting your crew to high g forces due to acceleration for months on end isn't going to be very good for them if not lethal.

It doesn’t take high acceleration. If you had a propulsion system that could do a sustained 1g acceleration a trip to Jupiter would take around 6 days, including deceleration. That is a quite reasonable transit time. There is just the small problem of finding such a propulsion system.

https://space.stackexchange.com/questions/840/how-fast-will-...

Absolutely. I think people don't really have a gut feeling for this, but you don't need high acceleration to get anywhere in the solar system; you just need sustained acceleration. Right now, our probes accelerate for minutes and then coast for years.

If you could sustain 1g acceleration for, say, weeks, it even makes interstellar travel reasonable. A day of 1g acceleration will get you up to about 850 kilometers per second... or, 73 million km per day. Thirty days of 1g acceleration gets you to 2 billion km/day. That's close to 1% of the speed of light.

We can build a fuel station on Moon, which will make pellets of fuel, then shot them in direction of a spacecraft at Moon orbit. Spacecraft can collect them, then fuel an ionic drive for constant acceleration for weeks. Moon has low gravity, no atmosphere, thus it makes it ideal for a railgun[0].

With a fuel station on Moon, it will be much cheaper to reach Mars, so it will be possible to build second fuel station at Fobos. With two fuel stations, it will be even cheaper to refuel a spacecraft for long-range missions.

[0]: https://www.space.com/36442-could-moon-miners-use-railguns-t...

Apollo and Artemis dose the expensive, fast trajectories due to protecting human life. There is a mission currently enroute to the Moon that will take months due to a frugal propulsion system.

Getting some heavy John Carpenter vibes with this Europa situation.

David Bowman is going to be pissed

> But the biggest surprise was the amount of water that the theoreticians needed to account for the signals: more than twice the amount of water found in all of Earth’s oceans. Because Europa is only a quarter of Earth’s diameter, the water must be spread around the moon in a global ocean, 25 to 95 miles deep, beneath a 10- to 15-mile-thick ice crust.

What is this fixation with water to see if Planet X supports life? Antartica would have been more habitable than Sub-sharan Africa if that was the case. What about the average surface temperature (it's -125C btw)? Gravity? Can it support Atmosphere ie, does it have a magnetic field? How much the round trip time be from Earth? Does it have anything at all that can sustain a farming ecosystem?

It's almost as if we just throwing darks in the dark just to find something. Maybe the conclusion is far more banal. There's nothing in the solar system, or maybe even in many light years, that will not be 100x harder to make habitable than least habitable regions of Earth itself.

The goal isn’t necessarily to find a second home, but to study extraterrestrial life.

Right now we don’t know if alien life exists and if it does how common it is, how similar it is to life on Earth, if it formed spontaneously, etc.

It would give us a second data point which we could use to calibrate our understanding of one of the greatest mysteries of our existence.

Afaik, current life ideas are all under-ice. Magnetic fields and surface conditions don’t matter, because Jupiter’s own magnetic field is a source of acute radiation. Callisto receives 7x Earth’s dose, but other surfaces are basically unhabitable.

> It's almost as if we just throwing darks in the dark just to find something. Maybe the conclusion is far more banal

The only way to know one way or the other is to prove it, which means sending exploratory missions on all the possible candidates for life nearby. Only THEN you can say that there is nothing. It's not a great scientific approach to stop because you're having doubts about your hypothesis.

And personally I do not care if it's a futile search or not, I just want to see high resolution pictures if not videos of Europa, its underground water, Titan and its methane lakes, and maybe Venus one day. I bet they would be even more mind blowing than the images we're seeing from Mars.

Venus surface images, for anyone who hasn't seen them: https://universemagazine.com/en/the-last-photos-from-the-sur...

Titan surface (not radar) images, for anyone who hasn’t seen them: https://photojournal.jpl.nasa.gov/spacecraft/Huygens%2BProbe

Sub-Saharan Africa gets massive amounts of rainfall, and Antarctica supports a pretty surprising diversity of life. You could well have a valid point but your "background points" are totally wrong, you'd be better just omitting them next time.

Moving on from that nitpick, have you actually tried to find out why water is considered a significant indicator for life? And is it really the case that other things such as what you've listed are overlooked?

Because we're looking for life of any kind. Water is the main ingredient to that as far as we know.

Water is a necessary component of life "as we know it," thus it makes sense that if we are going to find other life similar to life "as we know it," we're going to be inclined to check on places with water. That seems the opposite of throwing darts in the dark to me. A better metaphor is searching under the lamppost for our keys. We're inclined to search watery planets first because they seem like more straightforward candidates.

Farming and roundtrip time isn't immediately that important since, at least in the short term, there's no goal of terraforming or mining these moons. It's about trying to see if we can find signs of existing life, and to see if that will teach us something about life in general in the universe, or at least in our corner of it. For example, if we find something similar to DNA on Europa, that would be a point in favor of the panspermia hypothesis, or perhaps indicate that Earth's own microbes have been hitching rides all over the solar system via impact event ejecta [0]. On the other hand, if we find life but it's vastly different from Earth life, that would be a huge point in favor of life being ubiquitous throught the universe. Finally, even if we don't find any life whatsoever, because there is a water ocean, we might find chemical precursors to life or other interesting chemicals that could reveal to us something about how our own oceans evolved, geologically and chemically.

[0] https://www.liebertpub.com/doi/full/10.1089/ast.2013.1028

Living on land is kind of a niche activity that we take for granted given how many species here have perfected the art of legs and lungs.

Many more forms of life either live in ponds, walking ponds (us) or mega ponds (oceans).

Think of it as life coming in two forms: tiny stuff alongside big stuff, or just tiny stuff. The tiny stuff lives in water and in the absence of Europan antelopes, it’s the tiny stuff that we’re looking for.

There is simply an interest in answering the question

There are other parties interested in finding life in the least habitable parts of planet earth

If there was an area in the solar system beyond earth with either sub-saharic or Antartic conditions we would look there. This is the next best thing. So we look there...

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