When I first began the adventure of being a Geology / Environmental Geology student at the University of Arkansas, Little Rock, Arkansas, even though I had always been a "rock hound," and dug for fossils, the enormity of the Earth, and our Biosphere was hard for me to grasp.
Never before had my thinking been stretched to include the size of Tectonic Plates, or Geologic formations that are a history of what has gone on before.
Just to give you an inkling of the size of the Siloe Patera crater at the Arabia Terra region of Mars; I will hopefully give you something that can be measured in your mind.
In the U.S., if a person were to travel from Las Vegas, NV all the way to Tucumcari, NM, that is only 744 miles, or 1197 kilometers.
In Canada, it is 970 km from Vancouver, BC, Canada, to Calgary, AB. (About 603 miles).
In order for scientists to know for sure if this is a Caldera or damage from an asteroid, they would need funding to gather soil samples, to find the chemical make-up of the area affected by either event.