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. 1996Operation: 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 2003Operation: Jan 2004 - ?

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?