Astronomy190 - Topics in Astronomy Astronomy and Astrobiology Lecture 15 : Ancient Mars Ty Robinson

Questions of the Day What is the evidence for liquid water on early Mars? What was different about early Mars that made it possible for liquid water to exist on its surface? What processes have subsequently affected Mars’ ability to sustain liquid water on its surface?

Surface Ages

Evidence from Space I Mars Earth Mars Riverbeds

Evidence from Space II Mars Earth Mars Sedimentary Layers

Evidence from Space III Flooding

Evidence for Water I Satellite Images –Riverbeds –Sedimentary layers –Flooding Evidence for Water

Follow the Water

Mars Pathfinder Launch: Dec Operation: Jul-Sep 1997 Instruments: - cameras - weather sensors - rock analysis tools

Pathfinder Landing landing video

Evidence for Water II Satellite Images –Riverbeds –Sedimentary layers –Flooding Pathfinder –Maghemite –Flood plain Evidence for Water

Mars Exploration Rovers Launch: Jun, Jul 2003 Operation: Jan ? Instruments: - cameras - weather sensors - rock analysis tools - microscope

Landing Sites

Gusev Crater

Extended Mission

Landing Sites

Minerals from Space

Opportunity Landing Site

Extended Mission

Chlorine and Sediments

Evidence for Water III Satellite Images –Riverbeds –Sedimentary layers –Flooding Pathfinder –Maghemite –Flood plain Spirit –Silica deposits Opportunity –Sediments –Blueberries –Chlorine concentration Evidence for Water

Questions? Liquid water is not stable on the surface of modern-day Mars because… temperatures are too low surface pressure is too low both surface temperatures and pressures are too low water does not exist on Mars

Questions? What must have been different about Mars in the past so that liquid water was stable on its surface? thicker atmosphere thicker atmosphere with more greenhouse gases Mars must have had a stronger magnetic field Mars must have been closer to the Sun

Greenhouse

Summary

Atmospheric Escape Impact Erosion Photolysis Solar Wind

Questions of the Day What is the evidence for liquid water on early Mars? What was different about early Mars that made it possible for liquid water to exist on its surface? What processes have subsequently affected Mars’ ability to sustain liquid water on its surface?

Quiz 3 - What is one thing you did not understand from today’s lecture? 2 - Explain why increasing chlorine concentrations with depth in a crater is evidence for the existence of water there in the past. 1 - What are three pieces of evidence that point to a wet early Mars which can be seen from space?