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Mars Exploration

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)

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Mars Exploration

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  1. Mars Exploration Trey Smith November 9, 1999

  2. Overview • Mars Background • Exploration Missions • Focus on rovers • CMU space activities • Blue-sky plans for Mars 65 minutes, about 8 slides each

  3. 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

  4. Geological Map

  5. 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)

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

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

  12. 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

  13. 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

  14. 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.

  15. 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

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

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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 (?)

  22. 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

  23. 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

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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

  29. Space Initiative at CMU RI • 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

  30. Space Initiative at CMU RI • 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

  31. 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

  32. 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.

  33. 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 mission • Unfueled Mars Ascent Vehicle • Earth Return Vehicle • Nuclear reactor powered propellant plant • Two years later, with all the pre-launched components verified, astronauts take a fast (6 month) transfer orbit to Mars

  34. 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

  35. 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

  36. 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

  37. 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

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