61–70 of 74 posts
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Mars is smaller and cooled down before Earth. That means it had liquid water while the Earth was still too hot. Therefore, it's possible that life first appeared on Mars, and was later transferred to Earth on a meteorite.
Interesting. How would a meteorite pick something up in one planet to carry it to another planet? I'm presuming that the hypothetical meteorite does not originate in Mars.
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It's not that the water "blew away" in the solar wind, it's that the atmosphere did, taking the water vapor in the atmosphere with it. This is a very gradual process, which would happen on Earth too, if not for the magnetic field. I don't know that the collision with the moon is the secret here or not. I think it's complex.
Neither Venus nor Mercury have substantial magnetic fields presently (compared to Earth). I don’t know enough to know if that supports the GP’s conclusion or not, but it may.
Mercury has no magnetic field, and no meaningful atmosphere like we'd understand it. Venus has a minimal magnetic field, and is covered in hot dense CO2 layer because the solar wind blew away all the hydrogen and continues to blow away the atmosphere. The Earth has a much stronger magnetic field that has protected our oxidized hydrogen, and good evidence points to the giant impact hypothesis.
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I think the point still stands though, right? The moon is only 1% the mass of the Earth so if we had all that extra crust it wouldn't make our crust to core ratio so off that we couldn't have an atmosphere.
Read TSiege's correction again, it wasn't a (bad numbers) 1000T planet being impacted by a 10T object, it was a 500T object (earth) being impacted by a 500T object (now also earth) and ejecting a 10T object (now moon) from the debris. Without the event we'd have a planet even smaller than mars!
Mars lost all of its (surface) water presumably due to solar wind, and thus never had time to evolve complex life. Earth would have faced the same fate were it not for the fact that the Moon collided with us at some distant point in time, surrendering its iron core to ours. Now, our Rare Earth has an unnaturally large active iron core, resulting in an unnaturally efficient magnetic field which is able to protect our…
Just wondering, what would have stopped the Earth from having enough iron on its own in the first place? If the Moon could have that much iron, the Earth could as well have had it without needing to mix with the Moon, they're made from the same original matter after all.
https://phys.org/news/2017-12-doesnt-venus-magnetosphere.htm...
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Read TSiege's correction again, it wasn't a (bad numbers) 1000T planet being impacted by a 10T object, it was a 500T object (earth) being impacted by a 500T object (now also earth) and ejecting a 10T object (now moon) from the debris. Without the event we'd have a planet even smaller than mars!
I guess the question is rather than having 2 planets of 500T each form then collide, couldn't a single 1000T planet have formed from the same material?
Commented this and got flagged: “We need boots on the ground to back the good science behind these findings.” Why is wanting to send people to mars to confirm or leverage these findings so offensive?
Many, many single-purpose rovers can be sent in the place of a human mission with no risk to human life. There is no scientific justification for sending humans on a science mission, it's mostly just adventurism.
What also gets to me is that clearly people have done this cost-benefit analysis before - people that know a lot more about the topic than me. It lacks humility to ignore their reasoning (see https://spacenews.com/independent-report-concludes-2033-huma...).
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A batch of those people roll through every space related post and downvote things, but then the tide shifts later in the day. I'm pretty sure the vast majority of the users here are strongly in favor of getting humanity into space
> I'm pretty sure the vast majority of the users here are strongly in favor of getting humanity into space How do we turn this into a meaningful political movement? My strongest pro argument in a political context is resource security and not having to rely on adversarial states. Economically, it means and endless supply of sources we need to build our increasingly complex devices. Also jobs. I see this as an existen…
I feel like space investments are a lot more valuable than most of the stuff politicians care about nowadays, though, so I'd be interested to support a movement like that
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I have very little reason to believe life evolved in Earth or even in Mars for that matter. The more likely scenario is that there’s rocks floating around everywhere that have spores of life throughout the galaxy ready to seed a suitable planet in geologically instantaneous timelines. That will explain the extremely rapid emergence of life on earth initially while it took a few billion years to evolve any further. In…
That raises 2 problems for me. 1. How exactly are these spores of life getting into asteroids and being pinged around the Universe? The mechanism seems absurd to me. Earth is teeming with life, but outside of our explorations I believe none of it escapes our planet at all. 2. The life that would reach us would be already specialised for whatever environment it came from, and I would imagine would result a lower amout…
Remember that while you deal with insane numbers on the space side, viz. it’s emptiness, the number of planets etc., you’re meeting an insane adversary with biology as well. The number of cells in a single piece of sand in this planet is insane. The number of particles we might eject if there’s a catastrophic event from earth is insane. Anyone who worked on biology would know how hard it is to keep things truly sterile. I’m just extending it to outside space as well.
As for the conditions being too specific, while it’s true, I don’t see many outrageous combinations you can commonly observe in planets in the galaxy so I’m not sure if that’s a big deal breaker.
Commented this and got flagged: “We need boots on the ground to back the good science behind these findings.” Why is wanting to send people to mars to confirm or leverage these findings so offensive?
Many, many single-purpose rovers can be sent in the place of a human mission with no risk to human life. There is no scientific justification for sending humans on a science mission, it's mostly just adventurism.
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Seems like a bit of a stretch to say with certainty that Mars never evolved complex life 500+ million years ago.
Fair point, but even with rovers we have zero indication to the fact, and thus it's a very reasonable estimate.
Considering we believe this happened to earth, it's not unreasonable to think the same happened to Mars at least once.