During a hearing of the House Committee on Science, Space, and Technology Tuesday, Republican Congressman Dana Rohrabacher managed to baffle and amaze when he asked about life on Mars.
[...] "You have indicated that Mars had a, was totally different thousands of years ago," the California congressman said, addressing a panel of space science experts.
"Is it possible that there was a civilization on Mars thousands of years ago?".
[...] Kenneth Farley — NASA Mars 2020 rover project scientist — had to start off his answer by correcting Rohrabacher's question.
"So, the evidence is that Mars was different billions of years ago, not thousands of years ago," Farley said.
[...] "Would you rule that out? That — see, there are some people — well, anyway," Rohrabacher said.
Farley answered: "I would say that is extremely unlikely."
Source: Mashable
(Score: 1) by khallow on Saturday July 22 2017, @12:36PM (2 children)
Even so, why isn't there a sign of it on the surface of Mars? Erosion on Mars is quite a bit less than it is on Earth (almost no surface water and atmospheric pressure two to three orders of magnitude lower than Earth). Something like the Great Pyramids of Giza or the Great Wall of China would last a billion years on Mars. I didn't pick those examples because that's the technology level I'm expecting, but rather as an analogy to Earth projects of large size which have been around for a while.
Any structure on the surface which is say, 10 meters or greater in diameter would already be imaged by our current satellites orbiting Mars. Radar probing of the subsurface would pick up any openings to the surface and near surface structures (particularly hard stuff like metal buried in meters of sand). Between the two, we've found lots of evidence for natural lava tubes [wikipedia.org] and nothing for artificial structures.
(Score: 2) by Immerman on Saturday July 22 2017, @02:10PM (1 child)
Do you have actual calculations to back that up, or are you just speculating? Because I would imagine a billion years of erosion, tectonic activity, and meteoric bombardment would pretty much obliterate any surface artifacts - at least to the point where they'd no longer be recognizable as artifacts from orbital photography where each pixel is a couple feet across. Especially when you consider that the surface would likely have been abandoned thousands, possibly millions, of years long before surface water and microbial life disappeared.
And despite that, there actually *is* some evidence for potential artifacts on Mars - I remember when Google Maps first put up maps of Mars there was a big "anomaly identification" movement that found a lot of interesting things worthy of at least a little further investigation. A couple I remember offhand were things looking like long, extremely regular "drier vent hoses" half buried in sand winding across the surface (maybe some sort of geological formation? But what would cause that?) And, I think nearby, some fairly large geodesic-dome type structures that I can't think of any geologic source for. Crystals are about the only thing that naturally form facets like that, and even they very rarely form symmetric shapes, much less dozens of yards across. Pressure domes and tunnels on the other hand...
(Score: 2, Informative) by khallow on Saturday July 22 2017, @03:08PM
Most of the Moon's craters are more than a billion years old. For example, here's a guessimate map [wikipedia.org] for areas on the Moon that are a billion years or less old. So if Mars gets whacked as much as the Moon does, then most of its surface will be unmarred by asteroid impacts even a billion years later.
As to Mars geology, most of it is also thought to be over a billion years old. For example, from Wikipedia [wikipedia.org]:
So notice right there that volcanic activity has been nearly stationary for 3.7 billion years.
And as to wind erosion, the atmosphere is two to three orders of magnitude less dense than Earth's. As I recall, in some old Viking 1 photos (such as of "Big Joe" [nasa.gov], a nearby boulder), there are some signs of weathering, but not the extensive weathering that one would expect from wind activity. A study of this area has concluded [harvard.edu] that there hasn't been significant weathering of this area in roughly a billion years (I can't quote the text in question, which sites an older study, because it is an image).
So all of the potential, geologically significant processes known haven't affected Mars in at least a billion years.