I touch on the nature of sound on Mars in the first book, but this is new and a little wild. It’s not just the low pressure of the atmosphere that affects the transfer of sound. The composition of that atmosphere does as well. And it’s not the same across the range of sounds we hear.
From the article:
“Due to the unique properties of the carbon dioxide molecules at low pressure, Mars is the only terrestrial-planet atmosphere in the Solar System experiencing a change in speed of sound right in the middle of the audible bandwidth (20 Hertz to 20,000 Hertz)… The result of this is that sound travels more than 10 meters per second faster at higher frequencies than it does at low ones.”
Cas smiled. “Yep,” she said. She looked around. They were alone on the surface with no shelter other than their suits and the tent strapped to the SD Rover. Cas’s smile grew broader. “This is cool,” she said.
Hellas Planitia is an impact basin in the southern hemisphere of Mars. Impact basin is the term scientists use when they mean “really big crater,” and, as craters go, Hellas is huge. Mars has two of the largest impact basins in the solar system, and Hellas is one of them. The object that struck here, four billion years ago, was big enough to leave a crater 2,300 kilometers across and 7,152 meters deep. The tallest mountains of Earth could sit in the bottom of Hellas and barely peek over the rim.
Four billion years later, the impact of that object turned out to be critical for human existence on Mars.
Stop a moment and look at this image. The human eye loves a vanishing point image and this is a good one. Look at the way the tracks interact with features of the surface. Look at the other set of tracks to the right. Perseverance has been busy looking for just the right spot. Finally, look at Ingenuity, newly set on the surface of its new home, waiting for its chance to rise up and explore on its own.