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 map1894

The Good The Bad The Imaginative

What We Learned

• Polar Caps• Seasons• Atmosphere

Mariner 4

Launch: Nov. 1964Flyby: July 1965

~300km = 200miles

~300km = 200miles

Instruments: - camera - magnetometer

QuestionWhat can we learn?

What We Learned

• Atmosphere– Thin (~0.01 bars)

• Climate– Cold (-100 °C)

• Polar Caps– CO2 ice

– H2O 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. 1975Operation: 1976-1982

Instruments: - cameras - temp. sensors - wind sensors - seismometer - gas sensors

QuestionWhat can we learn?

What We Learned

• Geological Activity– None at present

• Polar Caps– CO2 ice

– H2O ice

• Atmosphere– Thin (~0.01 bars)

– Composition (CO2, N2, O2)

• 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. 2007Operation: Aug-Nov 2008

Instruments: - cameras - weather sensors - soil analysis tools

What We Learned

• Geological Activity– None at present

• Polar Caps– CO2 ice

– H2O ice

• Atmosphere– Thin (~0.01 bars)

– Composition (CO2, N2, O2)

• Weather– Dust storms

• Climate – Cold (-100 °C)

– T. Var’n (-140 to 30 °C)

• Sub-surface– H2O 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?