Humankind's earnest reconnaissance of Mars, made possible by advances in our technology, has progressed significantly over the past 150 years. Early ideas of vibrant macroscopic life on Mars in the late 19th and early 20th centuries gave way to a perception of a barren desert world whose overall long-term stasis was broken only by dust storms and predictable seasonal ice variations. Spacecraft from Earth first visited Mars in the 1960s and 1970s, and appeared to confirm that view.
Then came the twin Viking landers in the late 1970s, providing humankind with its first glimpses of Mars from a human-type perspective (i.e., at or near the surface, over timescales of minutes, hours, and days). The landers witnessed changes at their locations that from orbit were either easily misinterpreted or not detectable. The late 1990s and the first decade of the 21st century brought orbiting and landed spacecraft with new capabilities, along with more detailed Earth-based computer models, further confirming that many types of active processes are currently at work on Mars. Do we fully understand these processes? No. In some ways there are now more unanswered questions about Mars than there were three decades ago.
This talk will explore our current understanding (including some of my own atmospheric modeling work) of a selection of these phenomena, with emphasis on their human-relatable aspects.