Recent comments in /f/space

space-ModTeam t1_j96u8zz wrote

Reply to Fake memory about Halley's comet? by csarnoella

Hello u/csarnoella, your submission "Fake memory about Halley's comet?" has been removed from r/space because:

  • Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.

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kerfitten1234 t1_j96t87r wrote

Reply to comment by Gamingmemes0 in This image of Mars shows the north polar ice cap, the border between highlands and lowlands, former river valleys, plains covered by dark sands and the large Hellas Planitia impact basin in the south. Credit: ESA/DLR/FU Berlin by MistWeaver80

IIRC(applies to entire comment) mars rovers haven't actually been 'driven' since before MER. The rovers have rudimentary AI that takes instructions like "do science on that rock from this picture" and figures out how to do it, only needing humans for complex precise movements or troubleshooting.

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Gamingmemes0 t1_j96rbyv wrote

Reply to comment by Adialaktos in This image of Mars shows the north polar ice cap, the border between highlands and lowlands, former river valleys, plains covered by dark sands and the large Hellas Planitia impact basin in the south. Credit: ESA/DLR/FU Berlin by MistWeaver80

think about how hard it is to drive a car on a regular icy road.

Now make that road be made out of CO2 and water ice add in unpredictable terrain and then put the drivers seat in a room so far away it takes 15 minuites for inputs from your wheel for the car to respond.

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OlympusMons94 t1_j96r48u wrote

Reply to comment by djh_van in This image of Mars shows the north polar ice cap, the border between highlands and lowlands, former river valleys, plains covered by dark sands and the large Hellas Planitia impact basin in the south. Credit: ESA/DLR/FU Berlin by MistWeaver80

Atmospheric composition doesn't matter. Density does some for small objects, but any rock big enough to make the large craters visible in images like this won't be stopped by an atmosphere.

The Moon provides negligible shielding. It covers only a tiny portion of the sky. Hold out your little finger at arm's length. The Moon is half as wide (that's wide, not long) in the sky as that little finger. Imagine how good a shield that tip of your little finger would be. Well, the Moon is smaller and it's not at arm's length. It's almost 400,000 km away. Ther eis a lot of room in between.

Earth is also a much bigger target with much stronger gravity compared to the Moon.

Jupiter is about as likely to send objects toward Earth as divert them away.

Weathering, erosion, and covering with water and sediment (as well as vegetation) because of our thick atmosphere and water are important.

Besides that, Earth has a lot of volcanism to resurface face cratered areas. That is also why the dark lunar maria we can see on the Moon are so lightly cratered compared to the lighter surrounding highlands. The maria are giant plains of frozen lava. (Much of the maria surfaces are still really old, though. A relate dlld point is that there were a lot more eimpacts very early in the solar system's history.)

Lastly, Earth also has active plate tectonics, which deforms craters on land, completely subducts craters on the ocean floor within a couple hundred million years, and is related to Earth's volcanic activity.

Because of geologic activity, Venus, Europa, Enceladus, Io, and Pluto all have surfaces with few large or obvious craters. Their surfaces have all been resurfaced by lava or ice within the past few hundred million years.

u/Itis_TheStranger

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Brooksee83 t1_j96m2ci wrote

Reply to comment by Present_Reason2097 in This image of Mars shows the north polar ice cap, the border between highlands and lowlands, former river valleys, plains covered by dark sands and the large Hellas Planitia impact basin in the south. Credit: ESA/DLR/FU Berlin by MistWeaver80

Think of the surface as a pool of liquid and imagine a water drop landing in the pool. You typically see the middle pop back up after the original crater shape has fallen in. Link to a video example

Now realise that the surface is a solid being hit with something of immense energy. It will make a lot of the ground molten because of the energy, and act like the liquid example but will cool back to a solid in the process, so what you see is a slowing version of a droplet landing in a liquid, but eventually halting mid-formation because it's reforming as a solid.

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djh_van t1_j96ljrc wrote

Reply to comment by Itis_TheStranger in This image of Mars shows the north polar ice cap, the border between highlands and lowlands, former river valleys, plains covered by dark sands and the large Hellas Planitia impact basin in the south. Credit: ESA/DLR/FU Berlin by MistWeaver80

  • Our atmosphere protects us from a lot of the small and medium impacts by burning them up. Other celestial objects have either no atmosphere to do this (moon) or a very thin atmosphere that doesn't burn them up before impact (mars), or the wrong composition of atmosphere.

  • Often they don't have a climate to weather the impact craters that were made.

  • our moon acts like a giant magnet or deflector shield orbiting our planet and scoops up a lot of the objects that might otherwise have hit us.

  • the gravity of some of the bigger planets (Jupiter, Saturn) actually helps to deflect some of the more energetic objects coming from outside our solar system

  • the old impact craters are there, but they are ancient and our planet's life has covered them with vegetation and millenia of human activity.

  • and lastly, we've been very very very lucky in the last few hundred years. Nothing major has got through that obstacle course. But in recorded human history there have been a few biggies get through. Ancient records describe them, and even as recently as during the explorer days we've had records of asteroids coming in over some remote island or oceans.

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Itis_TheStranger t1_j96l9zk wrote

Reply to comment by [deleted] in This image of Mars shows the north polar ice cap, the border between highlands and lowlands, former river valleys, plains covered by dark sands and the large Hellas Planitia impact basin in the south. Credit: ESA/DLR/FU Berlin by MistWeaver80

Thanks for that explanation. I kinda figured it had something to do with the atmosphere. I know there are some impact craters on earth, but they are usually larger.

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space-ModTeam t1_j96hc65 wrote

Reply to so why don't earth slow down do to the drag of the water created in the tidel forces by the moon? by SnurrDass

Hello u/SnurrDass, your submission "so why don't earth slow down do to the drag of the water created in the tidel forces by the moon?" has been removed from r/space because:

  • Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.

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Subject_Meat5314 t1_j96h6lt wrote

Reply to comment by SnurrDass in so why don't earth slow down do to the drag of the water created in the tidel forces by the moon? by SnurrDass

Life on earth is already sustainable. The moon and earth will not reach the equilibrium you’re hoping for, but that’s not really related to sustainability.

Unfortunately, if you’re looking for perpetually life sustaining conditions, you’re out of luck. The sun is the problem. Stars have a life cycle and they don’t end well for life on their planets.

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