How long the Ancient Astronauts lived on Mars before things began to take a change for the worse is not known. But it could have be around 4 mya ago They did not see it coming at first when the first signs began to appear. There were already exploratory missions being sent to Earth as that planet had moved more into the habitable zone of the solar system while Mars seemed to be moving out of it. So they had to look after themselves in order to survive. They may have taken to the first steps to explore Earth around 3 mya ago and possibly making small outposts there.
Straddling the Northern Ocean boundary in Mars’ western hemisphere is a massive volcano-tectonic province known as the Tharsis region or the Tharsis bulge. This immense, elevated structure is thousands of kilometers in diameter and covers up to 25% of the planet’s surface. Averaging 7–10 km above the Martian “sea” level, Tharsis contains the highest elevations on the planet and the largest known volcanoes in the Solar System. Three enormous volcanoes, Ascaeus Mons, Pavonis Mons., and Arsia Mons (collectively known as the Tharsis Montes), situated and aligned NE-SW along the crest of the bulge. They had been active for some time. The vast Alba Mons(formerly Alba Patera) occupies the northern part of the region. The huge shield volcano Olympus Mons lies off the main bulge, at the western edge of the province. It was located in the Northern Ocean and had been active too- probably longer than all the others.
Olympus Mons was off the coast surrounded by the Northern Ocean
An area near these volcanoes was responsible for rift valleys and grabens- a portion of the Martian crust bounded on two sides by faults. This was an area where rock was being pulled apart by powerful tectonic forces. The tectonic plates on Mars were completely different than that of Earth and Mars is only about 1/3 the size of Earth. So the Ancient Astronauts were well aware of the area and had no colonies near it for those reasons, but they kept they eyes on as it would be a good area for another super-volcano to develop.
The Tharsis Bulge area from the ground
The first sign of trouble came at the Martian Equator the tectonic plates collided to where rocks were being pulled apart making an immense valley. Dust was thrown into the atmosphere and then came the Mars-quakes, up to 9.0 or more and the shaking could be felt for kilometers. Through tectonic plate action an immense system of deep inter-connected canyons and troughs began to form into what is now known as Mars' greatest riff valley the Valles Marineris.
Rift Valley formation always leads to Mars-quakes (or Earth- quakes on Earth)
A huge split in the surface of the planet began to open up creating canyons in some places 300 km wide and 10 km deep These deep canyons opened up ground for nearly 4000 km, nearly a quarter of the planet's surface and some Ancient Astronauts were misplaced from their communities by it and some may had lost their lives as well.
The length of the Valles Marineris is about same distance as it is from NYC to LA
Based on orbital observations and the examination of the Martian meteorite collection, the surface of Mars appears to be composed primarily of basalt. Some evidence suggests that a portion of the Martian surface is more silica-rich than typical basalt, and may be similar to andesitic rocks (a dark-colored volcanic rock composed essentially of plagioclase feldspar and one or more mafic minerals,such as hornblende or biotite) on Earth; these observations may also be explained by silica glass(sand). Much of the surface on Mars is deeply covered by finely grained iron(III) oxide dust today. This was the next sign of impending doom- the spread of the Iron dust in the atmosphere.
Current models of the planet's interior imply a core region about 1,480 km in radius, consisting primarily of iron with about 14–17% sulfur. This iron sulfide core was completely fluid then, and had twice the concentration of the lighter elements than exist at Earth's core. The core was surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but then was very active. The average thickness of the planet's crust is about 50 km, with a maximum thickness of 125 km. Earth's crust, averaging 40 km, is only one third as thick as Mars’ crust, relative to the sizes of the two planets.
Mars Current Atmospheric Situation (yellow indicates what is left of the magnetosphere)
Although Mars has no evidence of a current structured global magnetic field, observations show that parts of the planet's crust have been magnetized, and that alternating polarity reversals of its dipole field have occurred in the past. This paleomagnetism of magnetically susceptible minerals has properties that are very similar to the alternating bands found on the ocean floors of Earth. One theory, published in 1999 and re-examined in October 2005 (with the help of the Mars Global Surveyor), is that these bands demonstrate plate tectonics on Mars four billion years ago, before the planetary dynamo slowed down to a crawl and caused the planet's magnetic field to slowly fade away.
The Geology of Mars Today
But at the time when the Ancient Astronauts were living on the planet the core was completely fluid. There were plate tectonics and the planetary dynamo was beginning to wane but still providing the planet with a magnetic field that protected the atmosphere from the stellar wind and radiation from space. But as the dynamo began to slow down and the magnetic field of the planet began to weaken. The Ancient Astronauts noticed this almost immediately. Their scientists reported that the plates were slowing down but there was still volcano activity in the Tharsis region. Now these volcanoes seemed to be bringing the liquid core of the planet to the planet's surface. Erupting and blowing it's iron core into the atmosphere. This is one of the reasons you see so much granular iron oxide on the planet's surface today. It would only be a matter of time before the magnetic field faded and the atmosphere would disappear whisked out into space by the stellar wind.
History of water on Mars
The Ancient Astronauts had been surveying the Earth for some time as earlier indicated, and had come to the conclusion the planet may be ready for colonization. Time to check it again and see if it would now be the right place to migrate to. So that is what they did.
