Piscator

Hm ... cover a large area with soon to be freeze-dried egg powder ... let it mix with perchlorate dust ... then land a rocket. I see you thought about the "killing with fire" part already. In all seriousness though, I highly doubt we would be able to detect life on Mars by cultivation at all. And that's assuming we're employing a more sophisticated method than egging it. I'm not sure about the exact numbers, but I think it has been estimated that for each Earth microbe we can cultivate there are ten which we can't. On the one hand, there's the problem of figuring out the exact growth condition, which is tricky but solvable. On the other hand, there is the more serious problem of generation time. It's quite easy to cultivate an E. coli that replicates every half an hour or so, but what do you do if you're dealing with a hardy little critter that's adapted to a rather Spartan lifestyle and replicates once a year? Assuming optimum conditions of course, which typically don't involve a lot of egg. Considering the temperatures and the relative sparseness of nutrients, anything living close to the Martian surface would likely have a metabolism of the slow and steady kind, which would make any cultivation attempts very, very boring indeed. PS I don't see radiation and perchlorates as huge problems. Microorganisms can be extremely radiation-hardy and perchlorate is actually a bonus, since it keeps water liquid at low temperatures and can be metabolized quite easily.

Well, I think there was talk about using ground-based lasers (solar-powered in your scenario) to heat a rockets reaction mass to the necessary levels, but I don't know how seriously this can be taken. I guess heating the right parts and keeping the others cool might turn out rather difficult.

Kerbiloid mentioned quite an important point there. It is actually quite difficult to sterilize anything and I highly doubt it has been achieved for a spacecraft yet. Or even can be achieved. I remember from my university days that at one point planetary protection protocols involved rubbing down the spacecraft with alcohol soaked cotton swabs. Which kills some of the microorganisms but mostly just spreads them around. I assume, methods will have advanced from that quite a bit, but unless we build a spacecraft hardy enough to put into an autoclave, there's probably nothing we can do on Earth that's worse than exposing the stowaways to space/the Martian surface for a couple of months. And even if we do manage to kill 100% of viable germs, we will probably leave enough organic debris to interfere with our attempts to detect native life, so killing them is actually only half the job. Not sure what my conclusions are, but I guess there's very little we can do to avoid contamination entirely and we'll just have to design our experiments around this constraint.

Is it really considered likely that some random Earth germ that evolved under Earth conditions would somehow be able to outcompete native Martian organisms that lived and evolved there for millions of years? It's not like introducing rats to some remote Pacific island, it's like introducing rats to the middle of Antarctica. Contamination would certainly make the identification of native Martians a lot harder though.

Love the books, but I doubt that this particular scene would work as described even with Puppeteer tech. A thermal superconductor in contact with a liquid would ideed not get hotter than the boiling point of said liquid, but unfortunately it wouldn't remain in contact for very long due to the formation of a steam envelope. The superconductor would likely reach its thermal limits very soon and disintegrate, long before the steam has a chance to turn into something more spectacular like a rapidly expanding shell of plasma.

Or put another spacecraft in orbit around it and measure the period. Not practical? How dare you!?

I guess it would be possible that they're thinking about switching to a less complicated engine cycle (respectively a less complicated engine in general). Having a very high engine efficiency is obviously nice, but being cheap, reliable and easy to maintain might be worth more when all is said and done. This would also seem in line with the "the less parts the better" design philosophy.

I don't know if one seventh of a g instead of an eighth offers enough health benefits to counteract the effects of increased radiation exposure. Actually, since it's pretty much unknown whether lunar gravity levels offer that much of an advantage over no gravity at all, you might even choose one of the outer moons. After all, to reach Jupiter you'd likely have to spend a considerable time in microgravity anyway, so you'd probably be able to deal with it a bit longer. The ease of ferrying fuel, passengers and equipment from and to your base might very well be worth it. If you're after harvesting, let's call it "geothermal" energy for simplicity's sake, you'd probably want to be as much inward as you can be (also if you're trying to utilize Jupiter's magnetic field in some way) but again, I don't know if it's worth the increased radiation exposure in the end.

Wikipedia seems to support what I remembered: https://en.wikipedia.org/wiki/Muscle_architecture#Force_generation Muscle force is essentially proportional to the muscle's cross-section (an area) while the mass is of course proportional to the volume. A person twice as tall (yeah, yeah) would therefore have four times the muscular cross-section but weigh eight times as much. (Amusingly, the tall person would also have twice the body mass index, but that's a tangent.)

As far as I know, both grow exponentially, but with different exponents. Power increases quadratically while mass increases cubically.

Actually, a creature with bones made from osmium foam would rather benefit from small size. The strength/mass ratio of muscles decreases with size, so a cat-sized or even ant-sized organism would be substantially better off than a human-sized one. Apart from that, while high density bones seem at least marginally physically possible, high-density muscle on the other hand seems much less so. At the very least, I don't see how high density would offer any strength benefits. In other words, you either find another way to strengthen your muscles sufficiently to lug your 260ish kg of body weight around or you add some layers of regular muscle, which would probably create thermal issues from the fact alone that you would rapidly approach sphere shape.

Ah, wait ... are we talking about setting up the web cam on the lunar surface or at the Gateway? I was assuming the latter. Actually, you might not even have an uninterrupted view of Earth from a polar lunar surface base due to libration.

Well, one of the few things Gateway's proposed orbit is actually good for is providing an uninterrupted line of sight to Earth, so this would probably work quite well even without relay satellites.

The storage of genetic information is actually an area in which I would see a lot of room for diversity. You would likely need some kind of polymer made of pretty much the same chemical elements as DNA (as those are the most available und useful for this purpose) but after that, all bets are off in my opinion. After all, even earth life commonly uses two types of macromolecule with slightly different backbones and bases (DNA and RNA) and apparently it's not so rare to find bases other than the five regular ones in nature. (It seems even artificial ones have been successfully created and introduced into gene sequences.) If you consider that there are about 30 variations of the genetic code as well, it seems highly unlikely that life of extraterrestrial origin would use a system that would closely resemble ours. There seems to be too much room for variation.

Well, being able to reposition your sensory organs quickly and energy-efficiently has its advantages, especially for a species which relies on vision heavily but also has a rather narrow field of view.

In addition to what kerbiloid said, the appendix also seems to serve as a reservoir for gut microbes in case of ... severe discharge events. As for the main point of the discussion, I wouldn't say that life as we know it is the only option (in reality as well as in fiction) but as long as we're talking about chemical life some similarities are probably inavoidable. The number of elements suitable for building macromolecules is severely limited, so I would expect other forms of life to use them roughly in the same way and for the same purposes we do. On the other hand, even among known life there is a huge amount of metabolical pathways that could be used as a basis for speculation. There's - as has been rightly pointed out - quite a lot of exotic stuff going on right under our noses. In regard to the atmosphere first approach, it would probably have been a good first step to check what would make sense planetologically. A methane/oxygen atmosphere would be chemically unstable (possibly even explosively so). Same would be true for ammonia, hydrogen sulfide, hydrogen(!) and carbon monoxide in combination with oxygen. Basically any highly reduced and highly oxidized compounds would tend to react with each other over time, making the atmosphere more or less unstable in the long run. Large amount of noble gasses would also be tricky, since they are either quite rare in the universe or tend to get lost from the atmospheres of planets the size and position of earth due to their low molecular mass. For the same reason, hydrogen compounds would likely be quite rare on an earth-like world, even in the absence of free oxygen in the atmosphere. Hydrogen - freed by photochemical reactions - would steadily get lost to space. For a world comparable to our rocky planets, this leaves us basically with the classics: nitrogen, carbon dioxide and oxygen (if sufficiently replenished). It might get interesting again though, if we increase mass and/or the distance to the star.

Getting argon to react is indeed very difficult. More importantly though, it's completely pointless in the first place. Argon has no known role in "life as we know it", because forming those exotic flourine compounds is basically all argon can chemically do. It's not that earth life is somehow uncreative or not trying hard enough, it's the fundamental properties of argon that make it useless in biochemistry.

The "life as we know it" argument tends to be a bit overplayed in my opinion. With exactly one data point (and a still somewhat rudimentary knowledge of it), we simply can't tell if our kind of life is one of hundreds of wildly different arrangements or in fact the only type possible in this universe. While I don't consider the latter hugely likely, I would also guard against the "anything goes" approach. For every "hey, why not?" there's usually an "oh, that's why" and many of the ideas we consider plausible are simply a result of our lack of knowledge. (I'm looking at you, argon-fixating bacteria.) That said, it seems like a safe bet to assume that nitrogen would play an important role in the biochemistry of extraterrestrial life (the number of elements that can "combine with some reasonable amount of complexity" is surprisingly limited). I disagree though, that this would require huge amounts of diatomic nitrogen in the atmosphere, which is an exceedingly hard molecule to utilize biologically. Since molecular nitrogen is a rather convenient end product of metabolic processes involving nitrogen species, I would expect at least some build-up in the atmosphere (which would in turn give organisms an incentive to develop nitrogen fixation), but I'm not sure this would need to result in more than trace gas levels. I might be pushing the analogy too far, but after all, carbon-fixating organisms get by with very little carbon dioxide in the atmosphere too.

I think, the point was that the static fire is part of the quality contol scheme. Like, check your engines and your heat shield at the same time. This obviously only works if the tiles that came loose were actually faultily attached in the first place. If we repeat the procedure and a whole different set of tiles comes down, the attachment method definitely needs improvement.

I assume the atmosphere as a whole survives because it is constantly replenished, rather than because of the individual molecules staying around for any serious amount of time. There might be a gas torus effect though, in which escaping gas molecules remain in orbit around Saturn and occasionally return to the moon.

From context, I would assume that the tweet was made with more of a "megapixel" kind of resolution in mind, rather than the strict linear definition. That is, the idea seems to be to use a mirror with ten times the area of Hubble's which would fit nicely into a Starship hull.

Considering the much-discussed problem of perchlorates in the Martian soil, I find the claim that "there's no chlorine on Mars" a little surprising. (Sodium is present too, by the way.)

You wouldn't launch your rocket "straight up" though. Inclination doesn't mean the inclination of your launch trajectory in regard to the ground, but the inclination of the resulting orbital plane to the equator.

The problem seems to be that the non-magnetic cargo and/or passengers would be squashed flat.

You shouldn't forget that each use of your cannon imparts an impulse on it (opposite to the impulse imparted on the payload). That means that you'd either have to use propellant after all or cleverly time your shots in such a manner that your orbit remains stable, for example by firing in opposite directions or firing half an orbit later. PS The latter method (launching the payload in the same direction on opposite sides of your orbit) wouldn't work, as it would decircularize the orbit rather quickly.