The Space Thread

We're in business, ladies and gentlemen.

Jesus Christ, that's sensationalist as hell. Here's a more reasonable take.

tldr, a team announced that analysis of radar data may indicate that liquid brine (highly salty water) could exist if their assumptions about conditions are correct. Also, whatever it is, it's a kilometer and a half underground.

Which is still cool, but not "HOLY SHIT THERE'S DEFINITELY WATER ON MARS!" level.

Well, if liquid water can exist at the poles, nothing says there can't be deposits in warmer latitudes.

Future colonies may just end up mining underground water deposits the way we mine oil over here, just you wait.

Well, keep in mind that frozen water isn't all that hard to find on Mars, and all you have to do is warm it up. So already-liquid water wouldn't be all that valuable per se.

Especially if the already liquid stuff is hypersaline and needs to be distilled several times over before it's potable or useable for something like hydroponics.

Its more that, ever so gradually, the conditions required for life to exist on Mars keep adding up.

I've always wondered what would happen to the Earth's orbit if you suddenly removed different planets in the solar system. For example, Mercury is probably the least interesting of the rocky planets(at least to me). If Mercury suddenly vanished, how would Earth's orbit be affected?

Sounds like the start of an XKCD What If?

Unless that planet is Jupiter, almost nothing. Gravity is proportional to mass and by mass the entire Solar System is 99.9% the Sun, 0.01% Jupiter, Saturn is rounding error and the rest doesn't matter.

As far as gravitational effects go, absolutely nothing; with the possible exception of Jupiter which could manage to get all the way up to effectively nothing (seriously even at Jupiters mass the distance is so great there might be a few centimeters of orbital displacement).

We probably would get a significant uptick in comets and asteroids that get in systemwithout the gas giants to redirect them but that's about it.

Edit: Just calculated it; at closest approach Jupiter exerts enough gravitational pull to accelerate earth at 0.0000003675m/s squared; the absence of that would fall squarely into the absolutely nothing category.

Edited by Jaustin89* on Aug 1st 2018 at 10:14:52 AM

However, removing planets might induce long term changes in orbital patterns. They need time to add up however.

Lot's of time. I was thinking stuff like the Milankovitch cycles which operate on the scales of 100k years or more, and that's at least partly Jupiter's effect on the eccentricity of Earth's orbit.

I kind of wonder about what any theoretical aliens would do at the point in the future where the cosmic background radiation is gone and all the galaxies are so far away the light from one is never going to reach another. They'll justifiably believe that the entire universe is that single galaxy, so if they eventually conquer their galaxy what exactly are they going to do with further exploration? The galaxy will exist long enough that even at sub-light speeds they could probably discover every single planet and star, and catalog them down, so then what?

The cosmic background radiation will never disappear, it will just do what it's always done. Get more and more redshifted with ongoing expansion of the universe. It might get to the point where it's not practically detectable, but that will be long after the end of the stellariferous age.

And if every other galaxy is over your local event horizon, then it will be a case that the galaxy is your observable universe.

wouldn't the galaxy mostly be black holes, neutron stars/pulsars and white dwarfs by then?

Edited by alekos23 on Aug 3rd 2018 at 2:33:32 PM

I'm not totally clear on what the "Heat Death of the Universe" is exactly. I think it has something to do with all the heat having been dissipated so that everything is the same temperature? Like, there's no more "hot" or "cold" because all the heat in the universe has "leveled out" and there's no more flow from hot to cold because all the heat has already done that? I'm a bit unclear.

That's basically it. Another way you can think of it is that there's a finite amount of heat in the universe, and the universe is getting bigger, so eventually there won't be enough heat to fill it. Everything will be frozen (not just frozen like ice, but frozen like "has no heat at all") because a finite amount of heat divided by an infinite, expanding universe equals zero heat on average.

Well, I'm a bit hazy on the subject these days, but I've always considered Mercury to be rather interesting. It has quirks (relative to Earth, obviously) such as its years being shorter than its solar days and only slightly longer than its sidereal days. It's the atmosphere that's always fascinated me, however (the fact that it's constantly generating and losing atmosphere) and the fact that its scarps are so deep that it might be possible for ice to exist.

Am I remembering right in thinking that studying Mercury's motion around the Sun has been useful for a number of things, such as estimating the Sun's rate of mass loss and testing gravitational theories?

Edited by Wyldchyld on Aug 3rd 2018 at 7:47:55 PM

The precession of Mercury's orbit was one of the first big the first real big wins for explaining relativity, yes.

Precession is basically how the perihelion (point nearest to the sun) changes over time. All planetary orbits are slightly elliptical, with the planet moving slightly nearer to or further from the sun as time goes by. If you were to look down on the plane of the solar system from above and map any given planet's closest point to the sun, over several orbits you would notice it changing over time until it made a complete circuit.

Most of this can be explained purely using Newtonian laws of mechanics. Except for Mercury. The precession of Mercury's orbit is more than can be explained by Newton's laws. It's so close to the sun that there are extra effects explained by general relativity that have to be accounted for.

Edited by KnightofLsama on Aug 3rd 2018 at 8:22:58 PM

Precession! That's the word I wanted. Thank you!

I think I need to go back to school. I've forgotten so much science, it's shameful.

How often do Earth and Venus or Earth and Mars get the closest they can get to one another? Just out of curiosity

The School District for Dickinson, Texas has dedicated its recently built junior high school to native Eugene Kranz, best known for being NASA's Flight Director during the Gemini and Apollo missions.

As an alumni from that district, it's more hype to me than it should be, but still.

Edited by tclittle on Aug 6th 2018 at 1:53:21 PM

A quick google seems to suggest that it's roughly every 26 months for Mars, though there are several variables that govern exactly how close the approach will be. Same for Venus though it's about every 19 months. Very approximately.

Anyone know why the national solar observatory has been closed?

All I'm getting is conspiracies theories and it's not helping

Neil deGrasse Tyson was on Colbert last night and when asked about Trumps' Space Force, he said they already had one. It's called the United States Space Command and it’s under the auspices of the Air Force.