This document discusses the possibility of life on Mars, both in the past and present. It outlines some of the key challenges to life existing on Mars currently due to the lack of a protective magnetic field and atmosphere. However, evidence suggests Mars was once more hospitable. The document then discusses NASA's Mars 2020 mission which aims to return samples to Earth that could provide evidence of past or present Martian life through biomarkers, isotopic experiments with labeled substrates, or potentially DNA analysis if Mars and Earth life share a common ancestor. Contamination detection is a key challenge that must be addressed.

1. Life on Mars?
Dr. Rachel Mackelprang

2. Life on Mars
Does (did) it exist?
What might it look like?
Can we bring it home?

3. Central Questions
Does (did) it exist?
What might it look like?
Can we bring it home?

4. The Mars Environment: It’s Hard to Make a Living

5. The Mars Environment: It’s Hard to Make a Living

6. The Mars Environment: It’s Hard to Make a Living

7. Lost magnetic field and atmosphere
Lacks magne+c field, which would shield it from solar wind

8. Mars was more hospitable in the past
Artist’s concept of early Mars: https://www.nasa.gov/content/goddard/the-look-of-a-young-mars-2

9. Mars and Earth Timeline
Earth
and
Mars
Form
Start of
conditions
compatible
with life
First microorganisms
Mars
surface
becomes less
habitable
Oxygen
atmosphere forms

10. Did life exist on Mars?

11. Did life exist on Mars?

12. Did life exist on Mars?
It either adapted or went ex+nct

13. Could life exist on Mars?
Large underground lake below surface. Used low-frequency radar. Water is more
reflective. 12 miles across. Almost a mile below subsurface. Greenland & Antarctica
lakes found using similar techniques.

14. Central Questions
Does (did) it exist?
What might it look like?
Can we bring it home?

15. Life’s Universal Requirements
We assume all life must share a set of universal requirements
Create and maintain a cellular system Maintenance and Repair
Products
PotentialEnergy
ΔErxn
Ea_uncat
Ea_cat
Reactants
Catalysis
ATP
ADP P+
Energy in
Energy out
for cellular work
Use, transport, and
store energy
Adaptive Evolution

16. Sample Return Missions

17. Landing site selection
Jezero Crater: Water has filled and drained this crater many +mes.
NE Syrits: Ancient volcanic ac+vity
Columbian Hills, Gusev Crater: Mineral hot springs. Past floods, shallow
lake.

18. Landing site selection
Jezero Crater: Water has filled and drained this crater many +mes.
NE Syrits: Ancient volcanic ac+vity
Columbian Hills, Gusev Crater: Mineral hot springs. Past floods, shallow
lake.

19. Mars 2020: bringing samples back to Earth

20. Sampling and caching subsystems

21. Coring and sample tube

22. Coring and sample tube

23. Coring and sample tube

24. What should we look for?
Signs of PAST life
‘Hearty’ organic
molecules
Microscopic
fossils
Mineral
biosignatures: on
Earth, those that
are compositionally
and
morphologically
associated with life

25. What should we look for?
Signs of current or recent life
Least stable Most stable
DNA Proteins Lipids and
hydrocarbons
ka ma > ga

26. What should we look for?
Ac8ve microbial processes: isotope experiments
Labeled
Substrate
Headspace
gasses
Metabolic Activity
Viking Mission combined
isotopically labeled carbon
substrate and water. Monitored
the evolution of radioactive
gasses.
Gas production now thought to
be due to oxidizing agents in the
regolith—not life
Same rational for returned
samples, but use more realistic
substates, better controls and
instruments
Unlike DNA-based analyses,
does not assume a shared
common ancestor

27. What types of substrates?

28. DNA would be strong evidence of life
Relevant in the case where Mars and Earth life share a common
ancestor
DNA Isolation
DNA sequencing

29. DNA would be strong evidence of life
Relevant in the case where Mars and Earth life share a common
ancestor
DNA Isolation
DNA sequencing
We presume the transfer would have occurred in the distant past

30. DNA would be strong evidence of life
Relevant in the case where Mars and Earth life share a common
ancestor
DNA Isolation
DNA sequencing
We presume the transfer would have occurred in the distant past
Most recent
common ancestor
to life on Earth
Divergence prior to
most recent common
ancestor to life on
Earth
Earth
Mars
Use DNA sequence data to
determine relationship
between Mars and Earth life,
make inferences about
functional and survival
strategies

31. Detecting contamination
Predic8ng the rela8onship between Mar8n and Earth life

32. Detecting contamination
Predic8ng the rela8onship between Mar8n and Earth life
Most recent
common ancestor
to life on Earth
Mars samples
Earth samples
Genuine Mars life

33. Detecting contamination
Predic8ng the rela8onship between Mar8n and Earth life
Most recent
common ancestor
to life on Earth
Mars samples
Earth samples
Genuine Mars life Contamination