Astronomy/cosmology questions...

[Buster's Uncle]

Your language is good, but I'm going to need to teach you some news/journalism style.  You want to begin with a "lede", which is one sentence, concise as humanly possible without being misleadingly simple, with a summary of, and/or hook for, the article's idea(s).

Skimming the beginning, you need to say "astronomer Edwin Hubble" to avoid confusion with his eponymous space telescope.  At the mention of six months later for parallax. you probably ought to work in as briefly as possible that it's opposite side of orbit = greatest distance baseline.

I mean, in general, you want to cut where feasible, simplifying, but also idiot-proofing.

I'll try hard to give you an in-depth reading and a lot more feedback later today when I'm caught up on my daily routine.

Protip:  Always come up with a headline or two - not just for presentation here, but because even good editors sometimes come up with a head that misses the point and/or is a lame joke and/or chaps your butt some other way; it is standard practice to end you copy with some suggested headlines, which they may actually use instead of inventing something embarrassing.  Here, you'll want to bold your favorite at the top - but just as well get in the habit of putting any other head ideas at the bottom.

I should quote the journal link and these two posts to the dedicated thread, so we can go on from there there, shouldn't I?

[Buster's Uncle]

Lori, I imagine almanac stuff is not really in your wheelhouse, but - can you speak to the impression I've gotten over a couple years of feeding cats at sunset that the time changes enormously faster near equinox than solstice?

[Lorizael]

So are you referring to how fast the sun rises and sets? If so, then yes, it absolutely does so fastest at the equinoxes and slowest at solstices. At equinox, the run rises and sets exactly due east and west, so all of its (relative) motion is up and down. At other times, the sun's motion is at an angle, which means some component is not exactly up and down, so the rising and setting part is slower.

[Buster's Uncle]

I'm referring to how fast the length of the day changes.

[Lorizael]

I was going to answer that question first but then for some reason thought you might be asking the question I answered, then decided to answer both, then realized that would be convoluted and bloated and just answered the one question.

[Lorizael]

But again, yes, it changes fastest near equinox. If you think about this, it has to be the case. Just before winter solstice, the day is getting shorter each day. Just after solstice, it's getting longer. This can't be discontinuous, so the rate at which the amount of daylight changes has to go to 0 at the moment of solstice. The rest of the time it's going to be faster, with the fastest rates right in between the two solstices: the equinoxes.

[Buster's Uncle]

I thought it was something of the sort, but couldn't quite wrap my head until now.  Thanks, and thanks in advance from Momma.

[Rusty Edge]

Okay. Stumbled across this cool looking Mars terraforming video.
https://www.facebook.com/ScienceNaturePage/videos/1332147706917484/UzpfSTExNzM2NjM0MzkzNTIxMzk6MTk4MTYzNzg3NTIyMTM1NA/

This doesn't square with my concept of terraforming Mars. The usual explanation is that my concept of science is stuck in the Space Age.  Melting the icecaps would only result in two polar seas. Where are they getting the oxygen and hydrogen for oceans and atmosphere? Are they defrosting the perma-rust and then using plants to liberate the oxygen from the iron?

Don't get me wrong- I love the idea of terraforming Mars and always have, new worlds are full of possibility. But is this a possibility in want of commitment, or is it science fiction like the colonization project which hasn't worked out the critical problems yet?

[Lorizael]

I'll watch the video and comment when I get home from work, but honestly I get all my knowledge of terraforming Mars from:

https://boardgamegeek.com/boardgame/167791/terraforming-mars

[E_T]

Okay. Stumbled across this cool looking Mars terraforming video.
https://www.facebook.com/ScienceNaturePage/videos/1332147706917484/UzpfSTExNzM2NjM0MzkzNTIxMzk6MTk4MTYzNzg3NTIyMTM1NA/

This doesn't square with my concept of terraforming Mars. The usual explanation is that my concept of science is stuck in the Space Age.  Melting the icecaps would only result in two polar seas. Where are they getting the oxygen and hydrogen for oceans and atmosphere? Are they defrosting the perma-rust and then using plants to liberate the oxygen from the iron?

Don't get me wrong- I love the idea of terraforming Mars and always have, new worlds are full of possibility. But is this a possibility in want of commitment, or is it science fiction like the colonization project which hasn't worked out the critical problems yet?

Need a good Magnetic Field and Ozone layer so as to keep any real atmosphere that is released...  But it will last for a few millennium or so without...

[ColdWizard]

Yeah, I know, I kind of buried the lede there. It's mostly a computer job. I'm working for my university, helping NASA organize and archive data on small solar system bodies.

But what about the new thing on the block, 2015 BZ509? (An asteroid in a retrograde co-orbital resonance with Jupiter, recently asserted to be of possible interstellar origin). NASA's site didn't return any results when I searched for it.

[Lorizael]

I'll watch the video and comment when I get home from work...

I lied. Anywho, the problem with Mars is that it's dry and cold and has a thin wisp of an atmosphere. The bad news is there's no good way to directly combat either the dryness or the coldness.

If you melt the ice caps or bombard the planet with icy comets or setup an interstellar bucket brigade, the extremely low pressure means any liquid water more or less instantly boils away.

You also can't really increase the temperature because, well, what is it you're heating up? Not Mars itself--it's way too large. You just want a higher surface temperature, but there's barely anything on the surface to have a temperature.

The good news is both these problems can be solved by introducing an atmosphere. There is dry ice (frozen CO2) in the polar caps and probably some other greenhouse gases stuck in rocks. And the solar system is full of ammonia and CO2 and hydrocarbons that could be used to trap heat. Throw a whole lot of atmosphere onto the planet, trap heat, warm it up, melt ice, produce water vapor which is an extremely potent greenhouse gas, get yourself a nice positive feedback loop going on.

If you establish any kind of water cycle, the ice in the polar caps will eventually "fall" into the low-lying areas on Mars. (We see something similar happen on Mercury and Titan, for example.) There are questions about how much water is tucked away on Mars. May need to import more.

And Mars' lower gravity means you need a lot more atmosphere than that present on Earth to get the same surface pressure. And Mars' distance from the sun means it's just plain colder. May want to setup giant space mirrors to direct more light at the surface.

And yes, there's the problem that Mars' low gravity and lack of a magnetosphere means its more susceptible to atmospheric escape. Timescale on this is pretty long, but still something to worry about.

It's all pie in the sky right now. Transporting that much material through the solar system doesn't seem to be physically impossible, but we currently have no experience with any of that. How do you build a planet-wide magnetic field? How do you create a biosphere from scratch? How do you make sure you don't accidentally create Venus? No solid answers to those questions right now.

[Lorizael]

But what about the new thing on the block, 2015 BZ509? (An asteroid in a retrograde co-orbital resonance with Jupiter, recently asserted to be of possible interstellar origin). NASA's site didn't return any results when I searched for it.

You can either go to JPL Horizons and hit change Target Body or the Minor Planet Center and search there. This will mostly just bring up the Ephemeris data--position, speed, distance at certain times. Anything specific you want to know?

For what I do specifically, I help with the Planetary Data System (PDS) archive. We archive NASA mission data and other people who make proposals to store stuff with us. So we don't just have a generic listing of small bodies unless there's been some NASA-funded mission to look at some objects.

[ColdWizard]

Not specifically, since it seems there's a number of speculative theories and seemingly a need for better orbital data and extensive modeling. Tangentially, do you think Planet Nine exists?

[Lorizael]

I'm withholding judgment. Not a lot of evidence yet (a handful of KBOs with weird orbits), and not convinced there aren't observational biases in our detection so far (such that we're just seeing the weird ones right now but the population is distributed more or less randomly). Plus there are alternative theories, such as: https://www.youtube.com/watch?v=YW0Zb5gY0HA

(Wow I could not figure out how to embed...)