Red Rovers, Red Rovers,
Bring Martians on Over

Tonight's Journey

• Five decades of robotic exploration on Mars
• Key scientific discoveries that have reshaped our understanding
• The technological revolution from Sojourner to Ingenuity
• Current missions and the road to sample return
• Eugene Shoemaker's enduring legacy in planetary science

Eugene ShoemakerThe Father We All Share

• Co-founded planetary geology as a discipline
• Proved Barringer Crater was formed by impact (1960)
• Trained Apollo astronauts in field geology
• His impact crater studies became foundational to Mars surface interpretation

"The Moon is a record of the history of the solar system."

50 Years of Red Planet Exploration

• 1976 Viking 1 & 2 — First successful Mars landings
• 1997 Mars Pathfinder & Sojourner — First rover mobility
• 2004 Spirit & Opportunity — Extended exploration, water evidence
• 2012 Curiosity — Advanced geochemistry, habitable environments
• 2021 Perseverance & Ingenuity — Sample caching, aerial flight

Why Mars Matters

• Most Earth-like planet accessible for detailed surface study
• Preserves ~4 billion year record of planetary evolution
• Key questions Mars can answer:
• Did life arise independently on another world?
• What determines planetary habitability?
• What is Earth's future as a potentially drying world?

SojournerThe Little Rover That Could

• Landed July 4, 1997 — first Mars landing in 21 years
• Sojourner rover: 10.6 kg, ~65 cm long
• Total traverse: ~100 meters over 83 sols
• Demonstrated airbag landing system
• Alpha Proton X-ray Spectrometer (APXS) — first mobile geochemistry
• Engineering proof of concept for future rovers

Spirit & OpportunityThe Marathon Runners

• Landed January 2004 at Gusev Crater & Meridiani Planum
• 90-day design life → Spirit: 6 years / Opportunity: 15 years
• Opportunity traverse: 45.16 km — a marathon distance
• Science payload:
• Panoramic Camera (Pancam)
• Mini-TES, Mössbauer Spectrometer, APXS
• Rock Abrasion Tool (RAT)

Water, Water, Everywhere(Once)

Mars had sustained liquid water at the surface

CuriosityThe Mobile Laboratory

• Landed August 2012 in Gale Crater
• Nuclear powered (MMRTG) — no solar panel limitations
• Full analytical chemistry lab onboard:
• Sample Analysis at Mars (SAM)
• Chemistry and Mineralogy (CheMin)
• ChemCam laser-induced spectroscopy
• Mastcam imaging
• Still operating today, climbing Mount Sharp

An Ancient Habitable Lake

• Gale Crater: 154 km diameter, ~3.7 billion years old
• Evidence for long-lived freshwater lake:
• Fine-grained mudstones (Yellowknife Bay)
• Lacustrine (lake-deposited) sediments
• Circumneutral pH water
• All key requirements for life were present:
• Liquid water • Chemical building blocks (CHNOPS) • Energy sources

Reading Mars's Climate History

• Mount Sharp: 5.5 km of layered sedimentary rock
• Lower layers: clay minerals — wet environments
• Middle layers: sulfate minerals — drying conditions
• Upper layers: dust and wind deposits — modern dry Mars

Documents the transition from "warm and wet" to "cold and dry"

PerseveranceThe Sample Collector

• Landed February 2021 in Jezero Crater
• Primary mission: Collect and cache samples for Mars Sample Return
• Current status: 43+ samples collected
• Key instruments:
• Mastcam-Z (stereoscopic imaging)
• PIXL & SHERLOC (micro-scale mineralogy and organics)
• SuperCam (remote chemistry)
• MOXIE (oxygen production demonstration)

IngenuityFirst Flight on Another World

• 1.8 kg helicopter, technology demonstration
• First powered flight: April 19, 2021
• Completed 72 flights over nearly 3 years
• Total distance: ~17 kilometers
• Maximum altitude: 24 meters
• Flight duration: up to 169 seconds

Transitioned from technology demo to operational scout

Evolution of Mars Mobility

• 1997 Sojourner: 6-wheel rocker suspension, ~0.01 km/hr
• 2004 Spirit/Opportunity: Rocker-bogie, ~0.05 km/hr
• 2012 Curiosity: Scaled-up rocker-bogie, aluminum wheels
• 2021 Perseverance: Enhanced wheels, improved autonomy
• 2021 Ingenuity: First aerial mobility platform

InstrumentsFrom Hammers to Laboratories

Flying on MarsEngineering the Impossible

Future: Scout for rovers, access difficult terrain, sample retrieval

A 4-Billion-Year Archive

• Impact record: Craters preserve bombardment history (Shoemaker's legacy)
• Geological record: Stratigraphy records environmental change
• Volcanic record: Shield volcanoes document interior evolution
• Atmospheric record: Isotopic ratios reveal atmospheric loss

No plate tectonics = ancient surfaces preserved

The Case for Past Habitability

• Water evidence: Minerals (clays, sulfates, hematite), deltas, channels
• Organic molecules detected by SAM in Gale Crater:
• Complex organics in mudstones
• Seasonal methane variations
• Energy sources: Chemical gradients, potential geothermal activity
• Recent findings: Jezero delta shows potential biosignature textures

Mars's Chemical Diversity

• Igneous diversity: Basalts from primitive to evolved compositions
• Aqueous minerals:
• Phyllosilicates (clays) — water alteration
• Sulfates — evaporating water
• Carbonates — CO₂-water interactions
• Silica — hydrothermal systems
• Oxidation state: Variable, indicating changing conditions

From Warm and Wet to Cold and Dry

• Early Mars (>3.5 Ga): Warmer, wetter conditions
• Valley networks, deltas, lakes
• Greenhouse mechanism debated (CO₂? H₂? SO₂?)
• Transition (3.5-3.0 Ga): Atmospheric loss
• Solar wind stripping (no global magnetic field)
• MAVEN quantifying current loss rates
• Modern Mars (<3.0 Ga): Cold, dry, thin atmosphere

What We Still Don't Know

• Duration of habitability: Brief episodes or sustained eras?
• Organic preservation: How well do biosignatures survive billions of years?
• Subsurface water: Extent of buried ice and liquid aquifers?
• Volcanic history: When did volcanism cease? (Or has it?)
• Climate mechanism: What sustained liquid water under a faint young Sun?

The Challenges of Remote Geology

• Mobility: Rovers cover ~km/year; geologists walk km/day
• Instruments: No rover matches a terrestrial laboratory
• Communication: 4-24 minute delays; no real-time control
• Power: Constrains payload mass and operational tempo
• Risk aversion: Mission rules prevent exploring dangerous terrain

This is why sample return matters

Mars Sample ReturnThe Challenge

• Multi-mission architecture:
• 1. Perseverance (active) — sample collection
• 2. Sample Retrieval Lander — collect cached samples
• 3. Mars Ascent Vehicle — launch to orbit
• 4. Earth Return Orbiter — capture and return
• Estimated cost: $8-11 billion over ~15 years
• Partnership: NASA and ESA collaboration

No mission has ever launched from another planet's surface

Why Sample Return Changes Everything

• What returned samples enable:
• Isotopic dating — absolute ages, not crater counting
• Trace organic analysis — biosignatures at parts per trillion
• Microscopy — nanometer-scale imaging for cellular structures
• Future techniques we haven't invented yet
• Current status: Architecture under review
• Perseverance: Multiple depot locations established

The Next Decade of Mars Exploration

Commercial partnerships may accelerate sample return

Robots and HumansBetter Together

• Robotic precursors: Site selection, hazard mapping, resource identification
• Human advantages: Intuition, adaptability, sample selection, equipment repair
• Synergy model: Robots extend human reach, humans extend robot capability
• Key resources to characterize:
• Water ice locations • Dust properties • Radiation environment
• Timeline: Human Mars missions potentially in 2030s-2040s

Beyond Wheels and Rotors

Mars in ContextComparative Planetology

"Shoemaker's vision: Planets as experiments in geological evolution"

Mars and the Search for Life

Mars informs life detection on Europa, Enceladus, Titan, and exoplanets