That's beautiful.

Why do other planets, and moons have so many visible crater impacts? Earth doesn't have very many compared to Mars, or our moon.

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Looks amazing but why do the craters have protrusions at their centres?

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.

• 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.

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.

Silly question,but why didn't we send the rovers there,since on ice there is higher chance of finding maybe remnants of microbial life? Is it too cold/tech issue?

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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

If there is desert and ice, is there not water where the two meet somewhere?

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.

Yeah,makes sense.too bad.hopefully future tech will allow this

This image of Mars looks a lot like my wallpaper... now. Thanks!

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.

https://youtu.be/zufx28sBhWg

No, it's because of erosion and the fact that earth is tectonically active. Any meteor large enough to leave a decent crater isn't going to be stopped by an atmosphere.

FYI readditman is wrong. See my reply to their comment.

Mars is a cold desert, like Antarctica. Also mars' atmosphere is too thin to allow water to exist in liquid form on the surface, except in special circumstances.

Its my understanding that the frozen stuff sublimates into the atmosphere without spending much time sloshing around...

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Desert just means dry. All of it is frozen though.

Lol, your source is an opinion piece meant for kids.

https://www.britannica.com/science/meteorite-crater/The-impact-cratering-process

>Earth’s atmosphere certainly slows and prevents typical asteroidal fragments up to a few tens of metres across from reaching the surface and forming a true hypervelocity impact crater, but kilometre-scale objects of the kind that created the smallest telescopically visible craters on the Moon are not significantly slowed by Earth’s atmosphere...

The atmosphere shielding the surface is not the reason for that lack of craters on earth.

You can also see this easy in crater lakes like the huge one in Canada with a huge island in middle

I always wished i could get a good look at Uranus

Erosion, water and the atmosphere. The atmosphere protects the surface from some impacts, causing a larger number of small sized impactors to blow up in the air before reaching the surface and forming a crater. A similar effect happens with smaller impactors that hit the ocean and aren't large enough to make a crater in the ocean floor. The big factor though is erosion and plate tectonics. If you look at the surface of Mars most of that crust is ancient, billions of years old. On Earth the crust gets recycled constantly due to tectonics and volcanism. The big island of Hawai'i is a fraction of a million years old, for example, and the ocean floor keeps getting recycled in a process that keeps most of it under 150 million years old.

Then you have erosional processes due to the air, the water cycle, life, etc. Mountains get worn down, surface features get changed by rivers and shorelines, rocks get changed and moved around, life covers up or erodes surface features, etc. There's a huge crater in the Yucatan peninsula from the impactor that ended the reign of the dinosaurs 66 million years ago, but it's not easily visible to the naked eye because of all the erosional processes that have occurred since then. Remnants of older craters have been found but they are also not easily visible because of erosion. Smaller craters have a tendency to get completely erased by geological activity and erosion.

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Do we/will we have satellites orbiting mars for pictures? Id like to see the near street view of Mars

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

|Fewer Letters|More Letters| |-------|---------|---| |DLR|Deutsches Zentrum fuer Luft und Raumfahrt (German Aerospace Center), Cologne| |ESA|European Space Agency| |MER|Mars Exploration Rover (Spirit/Opportunity)| | |Mission Evaluation Room in back of Mission Control|

^(1 acronyms in this thread; )^(the most compressed thread commented on today)^( has 3 acronyms.)
^([Thread #8586 for this sub, first seen 19th Feb 2023, 20:33]) ^[FAQ] ^([Full list]) ^[Contact] ^([Source code])

Well, there's plenty of pictures of it on the internet, so enjoy ;)

Just heat up those poles and after some time you will have green house gas with thick atmosphere, it will bring back the rain and regulate the temperature

Earth has been hit by even more impacts than Mars has but because Earth has a thick atmosphere and strong weather systems the impact craters get weathered down until they are no longer visible or the the objects burn up in the atmosphere before hitting the ground.

Thank you for that reply. This is a great conversation and it's interesting to read the different information.

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Iridescent blue glow near North Pole? What could that be?

I’ve read a description before of Jupiter being described as a massive offensive lineman that protects Earth.

Do the remains of river valleys mean there was once water on Mars?

So many impacts. Is this due to the lack of atmosphere, that would normally cause most asteroids to burn up?

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I believe it to be high ice clouds.

yo..i see water in one of those craters..did i just discover water on mars?

It’s not that simple, unfortunately.

Mars lacks a magnetosphere, causing its atmosphere to be slowly stripped away by ionizing radiation from the solar wind. Even if you could provide the energy required to melt the ice caps on Mars, any resulting atmosphere would essentially be lost to space.

There was indeed liquid water on Mars in the distant past.

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A spacecraft was sent up there - https://www.nasa.gov/mission_pages/phoenix/main/index.html - and was able to establish ground truth for the existence of sub surface ice.

Many have advocated for that via a variety of different means.....and it's simply not enough

https://lasp.colorado.edu/home/maven/files/2018/08/Inventory-of-CO2-available-for-terraforming-Mars.pdf

There is not enough CO2 left on Mars in any known, readily accessible reservoir, if mobilized and emplaced into the atmosphere, to produce any significant increase in temperature or pressure. Even if enough CO2 were to be available, it would not be feasible to mobilize it; doing so would require processing a major fraction of the surface (analogous to regional- or planet-scale strip mining) to release it into the atmosphere, which is beyond present-day technology. Terraforming Mars is therefore not possible in the foreseeable future by utilizing CO2 resources available on the planet.

https://www.google.com/mars/

Yes! And if you notice the upper half of the picture looks like a dry ocean (you can see the high edge of a coast line). Now, one thing you notice is there are very few craters in that area that looks like it once had an ocean.

This is more evidence that this particular area was covered with water, which absorbed many of the impacts!

Amazing, absolutely amazing. Thank you so much for sharing!

That could mean so many things. Thank you!

Woah! Never knew that.thanks!

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What is the light blue wisps at the top and bottom? My research tells me that mars doesn't have a magnetic field, and though it has a faint aurora, it isn't directed to the poles.

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What does it look like without artists fixing the pic tho?

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No. We've known of the existence of water on Mars since before you learned how to type on a keyboard.

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The atmospheric loss is negligible on a human timescale though.

Is that true? I’m not aware of any planets lacking a magnetosphere that we’ve been able to actively observe losing an earth-like atmosphere to solar wind.

That is cool! How have I never heard about this? Thanks!

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Yep. The moment scientists spotted craters on Mars they knew it was a barren wasteland. Sad.

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The MAVEN spacecraft was sent to Mars to specifically measure the atmospheric loss rate. It is pretty low. The half-life of the Martian atmosphere is hundreds of millions of years. That's why it still has some atmosphere, and not vacuum.

Fortunately there are plenty of volatiles in the outer Solar System.

The warmest parts of the Martian surface are like the coldest places on Earth. Also the atmosphere is 95% CO2 and very little oxygen. Ordinary plants would not survive.

Can those results be extrapolated to a hypothetical Mars with an Earth-like atmosphere though? The atmospheric composition is quite different between Mars and Earth, after all.

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An Earth-like atmosphere would need to mass 27 tons per square meter on Mars vs 10 tons on Earth, due to the lower Martian gravity. That would be 3900 trillion tons total. Current loss rate is 95,000 tons a year. If the loss rate increased a thousand times to about 100 million tons/year. that still gives a half life of 20 million years, which is long by human standards.

There are several ways to reduce the losses. One is to put a magnetic shield "upwind" of the solar wind, and deflect it off the planet. That's effectively what Earth's magnetic field does.

Another is to dome the planet. Surface pressure depends on the weight of what is above the surface. It doesn't matter what that weight is made of. 27 tons is a lot per square meter. It would be more than 10 meters of glass thickness. So you can build a greenhouse the size of a planet and keep the atmosphere from leaking out.

Just because the top of an atmosphere being exposed to space is natural doesn't mean it is required. You can have several km of air below the dome to get an outdoor feeling, and leave the taller mountains sticking out into space if you want.

Definitely interesting, but unfortunately I doubt we will ever get the point of turning mars into a habitable planet. If anything, I think we will just make habitable shelters.

Thanks for the explanation!

Sorry to burst your habitat dome, but cool season grasses don't grow below 40F (4C). There are no trees or shrubs on Antarctica. The permafrost prevents root growth. The Curiosity rover which is near the equator, sees nighttime temperatures below -100F (-73C).

You can grow things under a temperature-controlled dome, but not out in the open on Mars today.

WE won't do anything substantial to Mars. The Martians will, once there are millions of them, if they have enough desire for it.

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