Astronomy190 - Topics in Astronomy Astronomy and Astrobiology Lecture 14 : Modern Mars Ty Robinson

Questions of the Day How has our understanding of Mars changed over the last 100 years? What did the Viking Biological Experiments tell us about the habitability of Mars’ surface? How has the Phoenix Lander influenced our perspective on the present-day habitability of Mars?

Perspective

Circa 1900 hand drawn map 1894 The GoodThe BadThe Imaginative

What We Learned Polar Caps Seasons Atmosphere

Mariner 4 Launch: Nov Flyby: July 1965 ~300km = 200miles Instruments: - camera - magnetometer Question What can we learn?

What We Learned Atmosphere –Thin (~0.01 bars) Climate –Cold (-100 °C) Polar Caps –CO 2 ice –H 2 O ice

Questions? Mariner 4 failed to measure a strong magnetic field around Mars. This is tells us… Mars does not rotate fast enough Mars’ composition is very different from that of Earth Mars is not within the Habitable Zone Mars does not have a liquid, conducting core

Questions? Mars does not have a liquid, conducting core. This tells us… Mars cannot support life Mars’ composition is very different from that of Earth Mars is geologically inactive Mars atmosphere is not volcanically-derived

Viking Landers Launch: Aug., Sep Operation: Instruments: - cameras - temp. sensors - wind sensors - seismometer - gas sensors Question What can we learn?

What We Learned Geological Activity –None at present Polar Caps –CO 2 ice –H 2 O ice Atmosphere –Thin (~0.01 bars) –Composition (CO 2, N 2, O 2 ) Weather –Dust storms Climate –Cold (-100 °C) –T. Var’n (-140 to 30 °C)

Viking Biological Experiments 1 - carbon assimilation experiment 2 - gas exchange experiment 3 - labeled release experiment 4 - gas chromatograph experiment

Carbon Assimilation = In the chamber…add Martian soil…and radioactive carbon… and water…and light. Evacuate the chamber and bake the soil to release volatiles.

Gas Exchange ++ = Controls: - add only water - perform experiment without light - bake the soil before the experiment Question What are some control experiments? In the chamber…add Martian soil…and nutrients. Monitor the gases inside the chamber through time.

Labeled Release ++ = Control = heat the soil first In the chamber…add Martian soil… and nutrients containing radioactive carbon. Monitor the gases inside the chamber through time.

Gas Chromatograph ++= Result : Martian soil contains even less organic material than Lunar soils returned by the Apollo astronauts. Life on Mars’ Surface In the chamber…add Martian soil…and bake. Look for organic- derived gases.

Mars Odyssey

Landing Sites

Phoenix Lander Launch: Aug Operation: Aug-Nov 2008 Instruments: - cameras - weather sensors - soil analysis tools

What We Learned Geological Activity –None at present Polar Caps –CO 2 ice –H 2 O ice Atmosphere –Thin (~0.01 bars) –Composition (CO 2, N 2, O 2 ) Weather –Dust storms Climate –Cold (-100 °C) –T. Var’n (-140 to 30 °C) Sub-surface –H 2 O ice

Phoenix Descent Heimdall Crater (10km Wide) Phoenix Lander parachuting to surface

Phoenix Landed heat shield parachute Phoenix

Phase Diagram Credit : Toby Smith

Mars Present-Day Habitability I

Mars Present-Day Habitability II

Methane?

Questions? If the methane on bars is due to life, the type of organism most likely responsible for creating the methane is… chemoautotroph chemoheterotroph photoautotroph photoheterotroph

Questions? Assuming chemoautotrophs are responsible for methane on Mars, what might explain the observations that methane levels vary seasonally?

Mars Overview Polar caps Atmosphere Weather Climate Subsurface ice

Questions of the Day How has our understanding of Mars changed over the last 100 years? What did the Viking Biological Experiments tell us about the habitability of Mars’ surface? How has the Phoenix Lander influenced our perspective on the present-day habitability of Mars?

Quiz 3 - What is one thing you did not understand from today’s lecture? 2 - Explain the arguments for why we might expect to find subsurface liquid water on Mars. What evidence do we have for this? 1 - In light of the Viking Biological Experiments, why do most scientists rule out the possibility of life on the surface of modern-day Mars?