Astro 202Prof. Jim Bell ([email protected])Spring 2008Lecture 25: Is/Was Mars Habitable?But first...Paper 7 is due at start of class on ThursdayPoster session is Thursday May 1That’s your final exam!No extensions!Be Ready!I will have poster boards for you today or ThursdayA few more words about your posters...Layout IdeasGosling, P., Scientists Guide to Poster Presentations, Kluwer, 139 pp., 1999 [Mann Library: Q179.94 G67x 1999]see also Purrington, C., “Advice on designing scientific posters,” Department of Biology, Swarthmore College; online at http://www.swarthmore.edu/NatSci/cpurrin1/posteradvice.htm• Poster should have a logical “flow” to it• Flow should be logical, like left to right, and/or top to bottom• Should be easy to “navigate”• Number/Letter various sections and/or use arrows, pointers, or other “linkage elements” if you anticipate any potential confusionCommon Poster “Blunders”Gosling, 1999• Title is larger than necessary• Titles that are too wordy and line spacing that is too large• Author’s names/affiliations/contact information are too small to read from afar• The text is overly wordy• Text type is too small or too large• Poster has a general lack of unity of style• Directional flow of information is not clear• Poster has poor composition (alignment, lines, flow, ...)• Poster uses too many small elements or too many small parts• Inadequate use of blank space (perhaps nonintuitive...)• Overpowering/distracting use of background graphics• Overzealous use of color• Poster elements mounted in unreadable positions• Use of unnecessary material• Poster is too big, too small, or the wrong shape for display board• Lack of attention once initiall mountedNASA's Astrobiology Focus!Searching for evidence of life in our solar system and beyond has become one of NASAs most important goals!It's not just words, it's actions...– Current Mars exploration program– Cassini/Huygens Titan entry probe– Europa Orbiter? Titan Orbiter? Enceladus?– Continued study of extreme life on EarthExobiology has a major role in Mars explorationFocus on Mars...The “Old” Mars...1900195616831986199920012003Viking OrbitersViking Landers?Is Mars just “the Moon with an atmosphere” – or –Was Mars like Earth long ago?Life on Mars?1Life on Mars?!Mars preserves clues that its climate may once have been very different...!...and that there is still a substantial (?) inventory of water at or near the surface...!...and that there is evidence for fairly recent volcanism and/or geothermal heat sources...Evidence for Life on Mars from a meteorite?!A small number (~20) of meteorites are thought to have come from Mars!Special one: ALH8400, found in Antarctica in 1984!Thought to be a sample of ancient Martian crust: radiometric age around 3.5 billion years!Cosmic ray exposure indicates ejection from Mars around 15 million to 20 million years ago!Outer chemical evidence indicates that it fell to Earth about 13,000 years ago3•Four pieces of evidence presented by scientists that ALH84001 preserves signs of past life on Mars:•Carbonate minerals: precipitated from a once thicker, warmer, atmosphere?•Magnetite grains: similar in shape to magnetite formed bacterially•Complex organic molecules: specifically PAH molecules•Segmented, "bacterial?" shapesLandmark paper published by McKay et al. (1996) Science, 273, p. 924Evidence for Life on Mars from a meteorite?4But much skepticism!!Is the rock from Mars?!Was it contaminated by Earth life while sitting in Antarctica for 13,000+ years?!There have been abiologic explanations proposed for each piece of "biologic" evidence!No "controls" on some new methods used!"Extraordinary claims require extraordinary evidence" --Carl Sagan!Proponents remain steadfast, despite criticism...5The real message of ALH84001!Whether or not ancient fossil microbes actually exist in this Mars meteorite may be secondary!ALH84001 and data from telescopes and space missions appear to show that:–liquid water existed in the Martian subsurface–complex organic molecules were there too–energy was provided by volcanoes, impacts, geothermal !The ingredients for life all appear to have existed at one time on Mars. Do they still exist today??The New Mars...23MGSMOCImaging25Gale CraterHighest point exceeds rim by ~1 kmHighest point exceeds rim by ~1 kmGale CraterGale Crater sedimentary deposits27Perspective view of exhumed channel in Gale...2829E04-01109M10-01713Sinus Meridiani Sedimentary Rocks• more diverse than at MER-B site! • erosional expression! • bedding properties! •"relative albedoCrater inMeridiani near 8°N, 7°W1000 mExhumed DeltaDiscovery of hematite in Meridiani PlanumMars Pathfinder!!XXX!!!X‘075 km!!XXX!!!X‘07...and most recently, Spirit & Opportunity51+ months of traverse by the Spirit rover...• Total distance: 7528 metersJan. ‘04BonnevilleColumbiaHillsHusbandHillSummitToday: Sol 1530HomePlateEl DoradoSol 381A“Peace”10 cmSol 431A“Paso Robles”10 cm10 cmSol 400A“Paso Robles”Water-relatedmineral deposits!Sol 381A“Peace”10 cmSol 167A“Pot of Gold”El DoradoSpirit Sol 708Dec. 30, 2005Southern Basin, on to Home Plateand then unexpected silica-rich soils!Spirit’s stuck wheelreveals unexpected sulfur-rich soils!Exploring “Home Plate”Sol 1530Yellowstone National Park??EnduranceVictoria!Erebus“Purgatory” sand trapToday: Sol 1509EagleJan. 2004Beagle50 months of traversing by the Opportunity rover...• Total distance: 11,692 meters1 cmWe found millions of “Blueberries”in the sand...And we found hundreds and hundreds of thin layers in salty rocks!EnduranceVictoria!Erebus“Purgatory” sand trapEagleBeagleOpportunitySol 690Outcrop rocks at Erebus5 cmMRO/HiRISENASA/JPL/U. ArizonaVictoriaCrater200 mEnduranceVictoria!Erebus“Purgatory” sand trapEagleBeagle200 mMRO/HiRISENASA/JPL/U. ArizonaArrived:September2006Alcove PanoramaCrater Panorama?A Year at VictoriaCraterCape St. MaryCape VerdeCabo FrioDuckBayBottomless Bay(Bahia sin Fondo)Bay of ToilBahia BlancaCape DesireCabo AnominoCabo CorrientesCape of Good HopeGolfoSan MatiasValleywithoutPeril(Cape St. Vincent)Rover todayOpportunity approaching Cape VerdeSol 1487 (March 30, 2008)?Is Mars just “the Moon with an atmosphere” – or –Was Mars like Earth long ago??• The New Mars is not just “the Moon with an atmosphere”• Craters and surfaces have been buried, exhumed, and re-buried many times•