Mars Exploration

1 Mars Exploration Trey Smith, Civilian & Military Apps in Space, Nov. 9, 1999

Mars Exploration

Trey Smith

November 9, 1999


Overview

• Mars Background

• Exploration Missions

• Focus on rovers

• CMU space activities

• Blue-sky plans for Mars

65 minutes, about 8 slides each


Mars Basics

• Most Earth-like planet (climate, geology)

• 6 millibar pressure of mostly CO2 at “sea level”

• Day length: 24 h 37 m• Inclination similar to

Earth’s (Earth-like seasons)

• Orbit period 1 year 10 months


Geological Map


Mars Geology

• Northern hemisphere– Mostly plains: young, low altitude

features

– Some are clearly volcanic, others attributed to sedimentation and action of sub-surface ice

– High points are volcanic plateaus of Tharsis (4000 km wide, 10 km high) and Elysium (2000 km wide, 5 km high)


Mars Geology

• Southern hemisphere– Highlands similar to those on

the moon, but craters are more eroded, and there are channels: evidence of running water.

– Just south of the equator, the Valles Marineris (400 km long, up to 600 km wide and 7 km deep) dwarfs the Grand Canyon

– Impact basins: Argyre (1800 km) and Hellas (900 km)

– Poleward of 30 degrees south, heavier erosion seems to indicate large quantities of ice


Mars Geology

• Chaos terrain– Jumble of broken blocks– Leads into large dry valleys, interpreted as

floodplains– Linear features at ends: lake shorelines?– Lack mature drainage system features– Floodplains were target of Viking 1 and

Pathfinder– Groundwater under extreme artesian

pressure?– Broken dams on large lakes?

• Other areas have small, more mature drainage basins

• Morphology of impact craters suggests ice everywhere at depths of a few hundred meters, closer to surface at poles


Climate History

• Erosion completely wiped out small craters and degraded others: process stopped about 3.5 Gyr ago

• Liquid water requires high temperatures. CO2 insufficient. CH4? NH3?

• Original water inventory estimated at 0.5 km over entire surface

• Isotopic studies suggest that up to 99% of Martian nitrogen, substantial CO2 and H2O went through nonthermal escape

• Some features younger than 3.5 Gyr (Elysium basin) have been attributed to shoreline wave action from a Northern ocean, but MGS found no such evidence

• In a few recent periods of high obliquity, conditions may have been warmer and wetter


Evidence for Life

• Requirements for Earth life: water, certain organics, and an energy source

• Likely environments:– Groundwater: energy source geothermal

– Ancient surface water

• Earth extremophile experts find bacteria everywhere they look: on bare rocks in Antarctica, in Yellowstone hot springs, hundreds of meters down oil wells.

• Earth life evolved less than 2 Gyrs into its 4.6 Gyr history, almost as soon as conditions made it possible

• Minority opinion says that Earth life first evolved deep underground using geothermal energy. Mars may have similar conditions

• Panspermia theory: life evolved once and spread through meteorite exchange.

• Mars cooled sooner, could have had life first


ALH 48001 (August 1996)

• Classified as a “SNC” meteorite based on isotopic ratio of trapped gases

• Three lines of evidence suggest life:– PAHs– Biominerals– Shapes like “nanobacteria”

• Findings widely criticized– Formation temperatures too high– No known nanobacteria on Earth– PAHs apparently resulted from post-

impact contamination

• Nonetheless, gave NASA its current Mars mandate


Mars Missions

• Pre-Viking space-race days• Viking and biology studies• Eighties doldrums• Current Mars mania


Pre-Viking Missions

• Mariner 4 (July 1965)– Five Soviet fly-by attempts failed, 1960-62

– Sister ship Mariner 3 failed on launch

– 22 pictures, 1% of the Martian surface

• Mariners 6 & 7 (July, August 1969)– 400 pictures of southern hemisphere and equator

– Studies of polar caps, moons, climate

• Mariner 9 (May 1971)– First US spacecraft to orbit another planet

– Discovered Mariner Valley, Tharsis volcanoes

– Mapped 100% of the surface and took high-res pictures of Mars’s moons


Pre-Viking Missions

• Mars 2 & 3 (May 1971)– Two orbiter/lander pairs

– Mars 3: First successful soft landing, but failed 20 seconds later

– Both orbiters continued returning surface and atmosphere images into 1972

• Mars 4, 5, 6, 7 (July, August 1973)– 4 & 5 were orbiters, 6 & 7 were landers

– Orbiters scout landing sites in advance

– Only Mars 5 meets mission objectives


Viking 1 & 2 (1975)

• Two orbiter/lander pairs

• Viking 1: First US landing on Mars (July 20, 1976)

• First took orbital images at 150-300 m resolution to select a landing site

• When the pictures came back, the ground crew thought the sky color was wrong and recalibrated.


Viking Biology Experiments• Pyrolitic Release (PR)

– Incubate soil in CO2/CO mixture tagged with C-14, pyrolize at 650 C; collect and combust any organic compounds and search for tagged CO2/CO

• Labeled Release (LR)– Incubate soil with C-14 tagged nutrient soup, look for evolved gases

• Gas exchange (GEX)– Measures production and uptake of CO2, N2, CH4, H2, and O2 using gas

chromatograph


Viking Biology

• Gilbert Levin, one of the investigators for the LR experiment, still believes life was found by Viking


After Viking

• Phobos 1 & 2 (July 1988)– Largely European instruments– US contributed DSN tracking– Carried surface “hoppers” for Phobos– Phobos 1 lost in transit, Phobos 2 lost just before

Phobos rendezvous

• Mars Observer (September 1992)– High-budget orbiter– Lost contact just before orbit insertion – Gamma ray spectrometer and other instruments

flew/will fly on later missions

• Mars 96 (November 1996)– European and US support– Orbiter, 2 landers, 2 penetrators– Crashed on Earth days after launch


Better, Faster, Cheaper

• After Mars Observer, NASA space science effort is demoralized.

• Two new (on-going) series of missions are initiated• New Millenium missions are test-beds for advanced

technology• Discovery missions have more conservative science

objectives, this time with a cost cap• ALH 48001 gives NASA a new mandate for Mars.

Missions are now planned at every launch window until 2005


Modern Mars Missions

• Mars Pathfinder• Mars Global Surveyor (November 1996)

– Orbiter now returning highest resolution surface images to date (3 meters)

– Also carries thermal emission spectrometer– Due to failed solar panel actuator aerobraking

took a year longer than expected. Primary mapping didn’t begin until March 1999

• Nozomi (July 1998)– First Japanese interplanetary probe– Orbiter to study atmosphere, plasma, dust,

possible magnetic field– Due to trajectory errors at Earth fly-by,

Nozomi won’t reach Mars until late 2003


Modern Mars Missions

• Mars Surveyor 98– Mars Climate Orbiter (Jan 1999)

• Intended to study Martian atmosphere

• Carried DS2 microprobes

• Impacted Mars due to software error in insertion burn September 23

– Mars Polar Lander (January 1999)• Surface imager, robot arm, thermal and

evolved gas analyzer

• Landing site is at the retreating edge of the ice cap

• Will land December 3


Reaching the Moon: Lunokhod

• Lunokhods 1 & 2 (November 1970, January 1973) were the first planetary rovers

• Teleoperated with echo time around 5 seconds

• Weighed in at 840 kg• Operated for 10 km (5 months) and

37 km (4 months)• Engineering accomplishments:

– Teleoperated control at lunar distances– Toilet-bowl thermal strategy– Drilling from a moving platform– Solved antenna pointing issue (?)


Reaching the Moon: Apollo

• The Lunar Rover was first used on Apollo 15 (July 1971)

• It weighed 462 lbs. empty• Loaded, it could move 10-12 kph for

about 50 km before exhausting its batteries

• Engineering accomplishments– Wheels and suspension successfully

adapted to regolith: each wheel driven independently

– Guidance: used an internal gyro and odometry to estimate relative positions, good to about 100 meters


To Mars: Pathfinder

• Launched Dec 1996, landed July 4, 1997. Operated for

• Engineering challenges:– 40 minute echo time, once-a-day

operations– Extremely limited power– Rocky terrain– Cold conditions

• Mobility sensors– Stereo cameras: dense stereo– Laser light striper


To Mars: Pathfinder

• Information integration on the ground– Registration of 3D meshes to form global

terrain map

– “Virtual Dashboard” allowed operators to visualize command results

• Operated through command sequence from ground, but could adjust for obstacles

• Not only successful, but also extremely popular

• Mars 2001– Orbiter carries GRS for elemental composition

– Lander will demonstrate ISRU propellant production with view to human missions

– Sojourner duplicate Marie Curie


Mars Autonomy: Athena

• 2003 and 2005 missions will form the two legs of a sample return (land in the same place)

• FIDO (Rocky 8) rover– Sojourner-style steering and

suspension– 1 meter scale– Stereo pairs pointing in all directions– Can elevate a mast to get longer view

• Goal: 100 meter traverse in one day of operations

• Can’t reliably see the intervening terrain – demands autonomy


Mars Autonomy at CMU

• Three year NASA program started last fall

• Studying software needed for 100 m scale traverse with a FIDO-like rover

• Two-prong approach:– Local obstacle avoidance: reactive

controller to dodge rocks

– Global path planning: slower planning of optimal path to goal using current information


Mars Autonomy at CMU

• First reduce stereo data to grid of goodness and certainty

• Local obstacle avoidance– For each steering arc, integrate goodness

and certainty of cells along the arc to get a score

• Global path planning– Uses D* (dynamic A*) algorithm– Scores a steering arc based on the path cost

from the end of an arc to the goal– Optimistically assumes uncertain areas are

traversable

• Both modules vote/veto to determine executed command


Space Initiative at CMU RI

• Icebreaker Discovery proposal to be submitted in March (for launch 2003)

• Lunar Prospector has detected hydrogen concentrations at the lunar poles

• The best explanation is ice in permanently shadowed regions like craters

• Icebreaker would travel in and out of permadark, verifying the presence of ice and assaying quantity, distribution



• Sky Worker• Nine month NASA grant from

space solar power program (demonstration in April 2000)

• Implementing a scaled-down prototype assembly, inspection and maintenance robot

• The prototype has 3 arms, walks hand over hand



• Robotic Antarctic Meteorite Search• 3 year NASA program, ends spring 2000• Attempts to autonomously find the next

ALH 48001. Final field test in December

• Visually identifies rocks and classifies them as meteor/non-meteor with a magnetometer

• Demonstrates teleoperation, endurance, autonomy capabilities needed for Icebreaker

• Uses local obstacle avoidance module similar to that of Mars Autonomy


CMU Astrophysics Projects

• Sloan Digital Sky Survey study– Looking for patterns in huge deep-

sky image databases

• Viper Telescope– Assembled in August in Antarctica

– 2 meter IR telescope resolves 0.1 arc-second features in cosmic background

– Also measures velocities of nearby galaxies relative to background, providing independent measure of H0


Blue-Sky Plans for Mars

• NASA has no long-term plan for human exploration.

• From the HEDS web site: Currently, NASA's efforts in human space flight are focused on the Space Shuttle and International Space Station Programs. Both of these programs are important to the development of a capability for human exploration beyond low-Earth orbit.


1997 Reference Mission

• NASA bowed to pressure from engineers both within and outside its ranks to create a mission design which cut costs and extended mission times using ISRU

• Based largely on Robert Zubrin’s “Mars Direct”

• 4 launch mission1. Unfueled Mars Ascent Vehicle

2. Earth Return Vehicle

3. Nuclear reactor powered propellant plant

4. Two years later, with all the pre-launched components verified, astronauts take a fast (6 month) transfer orbit to Mars


1997 Reference Mission

• Propellant plant uses water and Mars atmosphere: 2H20 + CO2 -> CH4 + O2

• Obstacles to development– No full-scale CH4/O2 thrusters

– A new HLLV is needed to launch each component

– Long-term effects of reduced gravity, radiation still not well understood (though probably not as dangerous as NASA would have us think)

• Overall, this is a very big mission and not on NASA’s political agenda right now


Cheap Launches

• The raw energy costs of launch from a planetary surface (Earth included) are on the order of < $1 per pound

• Here’s why it currently costs so much more:– Rocket equation: you need to carry your launch vehicle

and fuel, which wastes energy

– With expendables or high-maintenance reusable hardware, the bulk of the cost is in the launch vehicle assembly and maintenance

– Since each vehicle has never flown before, the risks are higher, leading to high insurance costs


Mars Beanstalk

• How do you get around all of these problems?• Don’t launch the launcher• On the moon you can use a mass driver• On Mars, you use a beanstalk• Part is above the geosynchronous orbit level, balances the part

below. Zero energy cost to stay in orbit• Now “launch” is just riding an elevator• An Earth beanstalk would require exotic materials like

“buckytubes” to handle the enormous tension• Lower Mars gravity allows current construction technology to

suffice.• In the future, Mars may be a supply station for asteroid

colonies


Terraforming

• Making other planets more Earth-like• Mars is probably the best candidate• Bring cometary water (greenhouse gas)• Darken the surface with engineered lichens• First habitable areas are deep in impact basins• Engineered plants can survive unprotected well

before humans• Mars land area approximately equal to Earth’s

Mars Exploration

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