Hi! I'm hoping this is the right place to ask this. I'm writing a novel for middle-school age kids in the vein of THE MARTIAN, and I'd like to make sure I'm not getting any major facts wrong. I'm pretty confident about most of these, but I'm in the middle of writing an afterword explaining some of the actual science behind various parts of the story, and it occurs to me that I'd really, really rather not publish a book where I tell kids that "Mars is X" when actually Mars is Y. If anyone here sees anything majorly wrong with these statements, can you let me know?1. Mars doesn't have a significant magnetic field, and so colonists on the surface would be exposed to dangerous radiation, especially during solar flares / CMEs. Also, compasses won't work.
2. Without an ionosphere, radio signals won't travel over the horizon, or even over large obstacles like a mountain (?). You would either need line-of-sight or would need to relay your signal through a satellite.
3. Phoenix found some of the first evidence for water ice in the soil on Mars. (Follow-up, though: we did know before Phoenix that the actual ice caps contained water ice, right?).
4. Airplanes and helicopters won't work because of the thin atmosphere.
5. An efficient mode of long-distance flight would be rockets, which would basically travel in ballistic arcs. During a trajectory like this, the occupants would be weightless on the way down. They would still experience normal gravity up until the highest point of the ballistic arc.
6. In theory, an air filter that sucked in CO2 from the atmosphere and converted it to O2 to breathe, meaning a person in an environment suit would only need to have a backup source of oxygen. I know rebreathers currently exist for SCUBA, but they seem to have a lot of limitations. My super-basic calculations are: Mars atmosphere is 0.5% Earth pressure; humans metabolize 5% of Earth air as oxygen and 'ignore' the rest by exhaling it; a perfect air filter would then need to suck in 10 liters of CO2 to get 1 liter of breathable air. I'm super-handwavy on this, I just want to make sure I'm not insane.
7. The most likely long-term source of oxygen for colonists would be water ice.
8. Mars doesn't have a north star, but in theory someone on the surface could tell true north by finding the point between several stars in certain constellations.
9. A dust storm of any significance would block out all (nearly all?) stars.
10. Stars on Mars don't twinkle because of the thin atmosphere.
11. Normal voices on Mars would sound extremely low-pitched because of the thin atmosphere. Humans could communicate acoustically suit-to-suit (via speakers/microphones), but they would need to modify the pitch of the sound to compensate.
Thanks for any help on this!chris
The polar caps were known to be primarily water ice prior to that thanks to various orbiters, though they also contain frozen carbon dioxide.
In the story, two kids are stranded during a solar flare that's destroyed all communication satellites.
Thank you!Out of all of these bits, the only one that concerns me, because it's a major plot point, is the question of whether communications over the horizon are possible in the absence of satellites. In the story, two kids are stranded during a solar flare that's destroyed all communication satellites. Eventually the kids find a radio with a directional antenna and climb to the top of a mountain so they can communicate with a colony that's just over the horizon.I'm fine that there are some obvious problems with this -- why do they need a separate antenna if normally their suits can talk to satellites? How could future satellite makers not shield well enough to protect from a flare? The main point is to get kids thinking about how ionospheres and the curvature of planets affect radio. But I would like to include an afterword that tells readers the parts that are farfetched or completely wrong.So, because I'm still not quite clear: if I'm in a pressure suit with a radio that normally communicates with satellites (or people nearby) and my friend is over the horizon, can the two of us talk? CuddlyRocket mentioned ground waves as a phenomenon that allows propagation even without an ionosphere. Is that enough to rely on when on Mars? Or, to put it another way: if you read a book with this idea, would you think "that's plausible, Mars's ionosphere does mean over-the-horizon communications might be impossible" or would you think "oh, boy, this author doesn't have a basic grasp of physics?"Regarding flight/ballistics: I didn't realize helicopters might work, thank you. I had read up on how airplanes would need enormous wings and/or need to fly ridiculously fast. So in my story, everyone flies in rockets in ballistic arcs. It's very amusing to me to think of 'normal' flight between cities/colonies involving weightlessness, especially since I can hardly stand to ride on fast roller-coasters. I appreciate the point about weightlessness after rockets shut off. I actually have it in the book this way, and then recently decided I must have misunderstood when I researched. My thought was that people on airplanes experience gravity when flying, and as long as the nose is pointed up, you could think of the plane as being in some kind of ballistic arc. I guess the difference is because of the lift exerted on the wings? Or is there something else I'm missing?I appreciate all of the input! If anyone happens to want to read the book, or pass it along to a 12-ish-year-old who might like it, email me at [email protected] and I can send you an electronic copy. Otherwise, wait for it to come out early next year, and then buy lots of copies... ;-)chris
6. In theory, an air filter that sucked in CO2 from the atmosphere and converted it to O2 to breathe, meaning a person in an environment suit would only need to have a backup source of oxygen. I know rebreathers currently exist for SCUBA, but they seem to have a lot of limitations.
I was surprised to see this slip by so many people.No. There is no such thing as a "filter" that turns CO₂ into O₂. Such chemical cracking of CO₂ into CO + O₂ is hugely energy intensive and will not be something done by a spacesuit.
Quote from: Paul451 on 04/06/2019 04:28 amThere is no such thing as a "filter" that turns CO₂ into O₂.For pure CO2, this is true. The atmosphere of Mars is not pure CO2, it has ~0.15% oxygen.[...]But a device to produce breathable air using 250W of power per person does not seem flat out ridiculous.
There is no such thing as a "filter" that turns CO₂ into O₂.