Aired LIVE from the S.A.G.A.N. THEATER!
Join us for a weekly broadcast of the Astrobiology Coffee Hour Seminars aired live on S.A.G.A.N. from Arizona State University.
Speaker: Casey Lisse
Title: Prospects for Life & Human Habitability Around Nearby Stars: Many Possible Homes for Our Elder(?) Race, But the Neighbors Are Likely Bacteria
Abstract: In this talk I will present the current big picture for the formation and evolution of life on Earth, with special attention given to the necessary astronomical, geological, and chemical requirements. Astronomically, there are 1011 stars in our galaxy, each according to the latest Kepler results likely to have formed its own Earth-sized planet. The Universe is 13.8 Gyr old, the Galaxy is about 12 Gyr old, our Sun is ~4.6 Gyr old, and high-Z chemical elements took a few generations of stars to form. Sol and our solar system are ~2/3 of the way out from our spiral galaxy’s relatively weak central black hole, in the suburbs. The Earth itself is a 4.56 Gyr old, highly differentiated, very unique object with all its water on the surface, a giant moon stabilizing its spin, and plate tectonics keeping it warm and shielded by a magnetic field. We live, work, & die on the thinnest wet rind of the orange: life is found on the Earth in an incredibly narrow spatial range, -20 to +100 km from the surface of a body of diameter ~104 km, and is found only where liquid water is available. Failed terrestrial planet harbors for life exist next-door in Venus and Mars.
Historically, the first forms of life appear to have formed in high temperature environments. Earth-life was mainly blue-green and single-celled for the first 3.5 Gyr of the planet’s existence. By ~2 Gyr, in the first massive life-based pollution event in the planet’s timeline, phototrophic plant life had driven the atmosphere out of equilibrium, removing almost all CO2 converting it into O2, without which there would likely be few animals and no land dwelling creatures. Complex multi-cellular life only arrived after ~3.5 Gyr. This multi-cellular life has gone through at least 4 huge upheavals and changes due to giant impacts: Bug Eyed Monsters, Trilobites, or Giant Lizards would be ruling the Earth without them. Creatures even remotely resembling H*** Sapiens have only been on the Earth for ~4 Myr out of 4.56 Gyr, an ~10-3 duty cycle. Bacteria, even today, are the most successful forms of life reckoned by total biomass, and we each carry some of this biomass on our skin, in our gut, and in our mitochondria.
Seminars are hosted by the ASU ''Follow the Elements'' Astrobiology team on Wednesdays at 8AM Pacific time.
You can view the seminar right here in the S.A.G.A.N. THEATER!