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Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

nasa.gov

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Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#121

Post by kjkjadksj »

jandrese wrote: post #89
holoduke wrote: post #74

Earlier quoted context omitted.

We just need a 1g rocket. Will take only a few days to get there. Life on earth will be 1000 years ahead once we are back though.

The problem is when you work out the math on rocket that can sustain 1G for multiple days with any Earthly isp you realize the math just doesn't work. Even if you go nuts and plug in a number like 1 million seconds (our best chemical rockets are more like 450 seconds) for the isp it is still nowhere close to feasible using only the mass of our solar system. As long as you are stuck flinging mass out of the back of yo…

Dyson proposed a fusion pulse propulsion system in the 1960s that was estimated at 70000 isp. Maybe 1m wouldn’t have been that far off from the limits of these crafts if test ban treaties didn’t kill their development.

Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#122

Post by kjkjadksj »

cout wrote: post #10

> These initial Webb observations also provided a possible detection of a molecule called dimethyl sulfide (DMS). On Earth, this is only produced by life. The bulk of the DMS in Earth’s atmosphere is emitted from phytoplankton in marine environments. Given a sufficient quantity of reactants/reagents, could DMS be produced via a natural process, or is this a sufficiently unfavorable reaction that it's unlikely?

It is produced industrially without needing life. I’m not sure why its the alleged smoking gun if theoretically if the conditions are right and the reaction is catalyzed it will go on without needing a lifeform.

2 CH3OH + H2S → (CH3)2S + 2 H2O

Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#123

Post by kjkjadksj »

marcosdumay wrote: post #44
cout wrote: post #10

> These initial Webb observations also provided a possible detection of a molecule called dimethyl sulfide (DMS). On Earth, this is only produced by life. The bulk of the DMS in Earth’s atmosphere is emitted from phytoplankton in marine environments. Given a sufficient quantity of reactants/reagents, could DMS be produced via a natural process, or is this a sufficiently unfavorable reaction that it's unlikely?

I don't think anybody knows enough to tell you what kinds of reactions happen on planet-wide environments without an oxidizing atmosphere.

Chemist certainly do. Reactions are carried out at specific atmospheric conditions. E.g. oxygen may well be purged.

Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#124

Post by mulletboy »

behnamoh wrote: post #24
v8xi wrote: post #14

In Nick Lane's Oxygen: The Molecule that Made the World, he talks about the importance of both methane and carbon dioxide and how they exist at the extremes of a complex metabolic oxidation-reduction cycle. Methane stores a lot of chemical energy in its C-H bonds which can be burned directly, or metabolized through repeat oxidation events to ultimately form CO2, which plants utilize with the help of the sun to form m…

I wonder what life looks like on a planet which is over 8 times more massive than the Earth. Do animals have spines at all on a planet with almost 8g gravity? Does life even get to evolve into complex systems like animals under this much gravity? How about plants? Do they grow up or spread out instead? If one day we get a visitor from this planet, they'll jump on our planet the same way human astronauts jumped on the…

Can anyone recommend a good book on exoplanets speculative biology, flora & fauna, etc?

Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#125

Post by lapama »

jandrese wrote: post #89
holoduke wrote: post #74

Earlier quoted context omitted.

We just need a 1g rocket. Will take only a few days to get there. Life on earth will be 1000 years ahead once we are back though.

The problem is when you work out the math on rocket that can sustain 1G for multiple days with any Earthly isp you realize the math just doesn't work. Even if you go nuts and plug in a number like 1 million seconds (our best chemical rockets are more like 450 seconds) for the isp it is still nowhere close to feasible using only the mass of our solar system. As long as you are stuck flinging mass out of the back of yo…

What about that strage propulsion system announced by caltech a few years back? Sorry really I have no more knowledge.

Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#126

Post by sgt101 »

wolverine876 wrote: post #97
edgyquant wrote: post #78

Earlier quoted context omitted.

Yes but we’re talking about before the Cambrian

? >>> Complex animal life took 3.5 bn years to emerge on Earth, >> How certain are we it took that long (the first time)? > Not certain at all, it’s based on last universal common ancestor estimates(LUCA) and supported by (lack of) fossil record. Do you mean, there's little evidence of pre-Cambrian absence? Absence of evidence is some evidence of absence, in this case. But how does LUCA fit into this question?

I think we can see where different complex animals split in their evolutionary tree - so humans and starfish split a long way back. Then we use a standard mutation clock to estimate how long ago that was. If all complex animals split from simple animals an estimated 700m years ago...

Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#127

Post by mcv »

Aachen wrote: post #21
Jeff_Brown wrote: post #20

In case you wondered too, this is 124 light-years from us.

Wow, that's really close so far as these things go. With the nearest star being 4ly, this can be reached with essentially the same tech level if we'd want to visit that with a rover or generational ship one day

> this can be reached with essentially the same tech level

I'm not so sure about that. I mean, at the moment both are impossible, but it's much easier to imagine traveling 4ly than 124ly. 4ly can be reached in a single lifetime if you accelerate a shop to .9c, which is technically possible. 124ly is going to be a multigenerational undertaking no matter what. The 248y communication lag is also a much bigger obstacle than an 8y lag.

I think once you can travel 124ly, you can travel 1000+ ly. You need to be completely self-sufficient and you're going to lose contact with home anyway. If you send a robot, you're not going to hear from that robot again in centuries, if ever.

Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#128

Post by marcosdumay »

kjkjadksj wrote: post #123
marcosdumay wrote: post #44

Earlier quoted context omitted.

I don't think anybody knows enough to tell you what kinds of reactions happen on planet-wide environments without an oxidizing atmosphere.

Chemist certainly do. Reactions are carried out at specific atmospheric conditions. E.g. oxygen may well be purged.

Chemists do controlled reactions in controlled environments. It's a completely different thing from knowing what happens somewhere in a planet.

Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#129

Post by ericbarrett »

ethbr1 wrote: post #114
ericbarrett wrote: post #83

Earlier quoted context omitted.

Earth's surface gravity is really on the edge of what's feasible for chemical rockets; IIRC the limit is around 1.4g. Though as other commenters have mentioned, it's possible to have a much more massive planet that's also got a larger radius and thus has comparable surface gravity. Some fun trivia—the planet Kerbin from Kerbal Space Program is the opposite case. It has a radius of 600km, versus Earth's 6378km, but is…

To expand, isn't that limit "the most efficient possible chemical rockets, launched from sea level"? I.e. air-breathing aircraft + chemical rockets would work, as would other exotic solutions

I think an air-launched rocket would only be an incremental help. Chemical rockets on Earth are barely at 1/8th of orbital speed before they're out of most of the atmosphere (~60km altitude). You can't accelerate more without ascending because drag increases exponentially with velocity at a given air density.

Another way of looking at it—on a body with no atmosphere, the most efficient way to attain orbit is to be on the equator, point your spacecraft "east" (prograde to rotation), and elevate the nose just enough to avoid lithobraking on that mountain in the distance. If Earth were such a beast it would take roughly 7000 m/s delta-V to do this. IRL, because you need to get over the atmosphere first, it takes about 9000; the "gravity turn" is a compromise between losing energy to gravity/steering versus losing it to drag. So any exotic system—air launching a Saturn V is definitely exotic!—would help with efficiency, but I don't see that it would radically alter the situation.

Re: Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18B

#130

Post by ethbr1 »

ericbarrett wrote: post #129
ethbr1 wrote: post #114

Earlier quoted context omitted.

To expand, isn't that limit "the most efficient possible chemical rockets, launched from sea level"? I.e. air-breathing aircraft + chemical rockets would work, as would other exotic solutions

I think an air-launched rocket would only be an incremental help. Chemical rockets on Earth are barely at 1/8th of orbital speed before they're out of most of the atmosphere (~60km altitude). You can't accelerate more without ascending because drag increases exponentially with velocity at a given air density. Another way of looking at it—on a body with no atmosphere, the most efficient way to attain orbit is to be on…

This seems to work through the numbers and equations, albeit for answering a slightly different question: https://space.stackexchange.com/questions/20054/fuel-needed-...

In summary, as you said, the altitude is less important than the base velocity increase and atmospheric density reduction.

The former, because you're pushing maximum mass at t=0 (i.e. all the future fuel you need to burn), so any added velocity at rocket ignition time would compound throughout the rest of the burn cycle (or, to think of it another way, you've already overcome fully-fueled vehicle inertia with the benefit of atmospheric oxygen combustion).

Similar to how a multistage vehicle operates more efficiently, albeit without the benefit of atmospheric oxygen.

The latter, because you're essentially getting atmospheric density reduction for "free" (in terms of saving your on-vehicle propellant), and your propellant efficiency (in terms of propellant:velocity increase) scales better.

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