Water On The Moon Essay Research Paper
Water On The Moon Essay, Research Paper
Abstract The Pentagon announced on December 3rd, 1996 that dataacquired by the Clementine ballistic capsule indicates that thereis ice in the underside of a crater on the Moon. Located onthe Moon & # 8217 ; s South Pole it was discovered with radio detection and ranging informations. Introduction & # 8220 ; The Deep Space Program Science Experiment ( DSPSE ) , thefirst of a series of Clementine engineering demonstrationsjointly sponsored by the Ballistic Missile DefenseOrganization ( BMDO ) and the National Aeronautics and SpaceAdministration ( NASA ) , launched in early 1994. It & # 8217 ; sprinciple aim is to infinite measure up lightweight imagingsensors and constituent engineerings for the following generationof Department of Defense ( DoD ) spacecraft. & # 8221 ; ( Sweeney, 1998 ) The Clementine mission uses the Moon, a neat-Earth asteroid, and the ballistic capsule & # 8217 ; s Interstage Adapter ( ISA ) as marks todemonstrate lightweight constituent and detector public presentation. As a secondary mission, Clementine returns valuable informations ofinterest to the international civilian scientific sector. It represents a new category of little, low cost, and highlycapable ballistic capsule that to the full embrace emerging lightweighttechnologies to enable a series of long continuance deep spacemissions. Background: The Clementine Spacecraft: The BDMO assignedresponsibility for the Clementine ballistic capsule design, industry, integrating, and mission executing to the NavalResearch Laboratory ( NRL ) . Clementine launched on a TitanIIG expendable launch vehicle from Vandenburg Air Force Baseinto Low Earth Orbit in January 1994. During its two monthorbit of the Moon it captured 1.8 million images of theMoons surface. The Lunar Prospector: After the find of thepossibility of H2O on the Moon, plans such as NASA andDSPSE began work on an extended undertaking called the LunarProspector. The Lunar Prospector is designed for low polarorbit probe of the Moon, including mapping ofsurface composing and possible polar ice sedimentations, measurings of magnetic and gravitation Fieldss, and survey oflunar outgassing events. Datas from the 1 to 3 twelvemonth missionwill allow building of a elaborate map of the surfacecomposition of the Moon, and will better our understandingof the beginning, development, current province, and resources ofthe Moon. The ballistic capsule is a graphite-epoxy membranophone, 1.4meters in diameter and 1.22 metres high with three radialinstrument roars. There is no on-board computing machine, groundcommand is through a 3.6 kbps ( kilo bytes per second ) telemetry nexus. Entire mission cost is about $ 63 million. After launch, the Lunar Prospector had a 105 sail to theMoon, followed by interpolation into a near-circular 100 kmaltitude lunar polar orbit with a period of 118 proceedingss. The nominal mission continuance is one twelvemonth. A two yearextended mission following this is possible, during whichthe orbit will be lowered to 50km and so 10km height toobtain higher declaration measurings. On March 5th, 1998: On March 5th, 1998, it was announced that informations returnedby the Lunar Prospector ballistic capsule indicated that H2O iceis nowadays at both north and south lunar poles, in agreementwith Clementine consequences for the south pole reported inNovember 1996. The ice originally appeared to be assorted inwith the lunar regolith ( surface stones, dirt and dust ) atlow concentrations cautiously estimated at 0.3 to 1percent. The ice was thought to be spread over 10,000 to50,000 square kilometres of country near the north pole and5,000 to 20,000 square kilometres around the south pole, butthe latest consequences show the H2O may be concentrated inlocalized countries instead than being spread out over theselarge parts. The estimated entire volume of ice is 6trillion kilogram. Uncertainties in the theoretical accounts mean this estimatecould be off well. How was the ice detected: The Lunar Prospector, a NASADiscovery mission, included a experiment called the NeutronSpectrometer. This experiment is designed to observe minuteamounts of H2O ice at a degree less than 0.01 % . Theinstrument concentrated on countries near the lunar poles whereit was thought these H2O ice sedimentations might be found. The
Neutron Spectrometer looks for alleged & # 8220 ; decelerate & # 8221 ; ( or thermal ) and & # 8220 ; intermediate & # 8221 ; ( or epithermal neutrons ) which resultfrom hits of normal & # 8220 ;
fast” neutrons with hydrogenatoms. A significant amount of hydrogen would indicate theexistence of water. The data showed a distinctive 4.6percent signature over the north polar region and a 3.0percent signature over the south, a strong indication thatwater is present in both these areas. How can ice survive on the moon: The moon has no atmosphere, any substance on the lunarsurface is exposed directly to vacuum. For water ice, thismeans it will rapidly sublime directly into water vapor andescape into space, as the Moon’s low gravity cannot hold gasfor any appreciable time. Over the course of a lunar day(29 Earth days), all regions of the moon are exposed tosunlight, and the temperature of the moon in direct sunlightreaches about 395 degrees K (or 250 degrees above F). Soany ice exposed to sunlight for even a short time would belost. The only way for ice to exist on the Moon would be ina permanently shadowed area. The Clementine imaging experiment showed that suchpermanently shadowed areas do exist in the bottom of deepcrater near the Moon’s south pole. In fact, it appears thatapproximately 6000 to 15,000 square km of area around thesouth pole is permanently shadowed. Much of the area aroundthe south pole is within the South Pole-Aitken Basin (shownabove with large arrow pointing to it), a giant impactcrater 2500km in diameter and 12 km deep at its lowestpoint. Any water ice at the bottom of the craters couldprobably exist for billions of years. Where did the ice come from: The Moon’s surface is continuously bombarded bymeteorites and micrometeorites. Many, if not most, of theseimpactors contain water ice, and the lunar craters show thatmany of these were very large objects. Any ice whichsurvived impact would be scattered over the lunar surface. Most would quickly vaporize by sunlight and lost to space,but some would end up inside the permanently shadowedcraters, either by directly entering the crater or migratingover the surface as randomly moving individual moleculeswhich would reach the craters and freeze there. Once insidethe crater, the ice would be relatively stable, so over timethe ice would collect these “cold traps”, and be buried tosome extent by meteoritic gardening. Such a possibility wassuggested as early as 1961 (Watson, 1961). However, loss ofice due to photodissociation, solar wind sputtering, andmicrometeoroid gardening is not well quantified (Arnold,1996).Discussion and Summary:Is there any other evidence for ice? Arecibo regions seem to indicate that water ice is the mostlikely possibility. However, Arecibo radio telescopestudies using the same radio frequency as Clementine showedsimilar reflection patterns from areas which are notpermanently shadowed. These reflections have beeninterpreted as being due to rough surfaces, and it wassuggested that the Clementine results may have been due toroughness, rather than water ice, as well. Why is ice on the Moon important: This ice could represent relatively pristine cometaryor asteroid material which has existed on the Moon formillions or billions of years. A robotic sample returnmission should bring ice back to Earth for study, perhapsfollowed by a human mission for more detailed sampling. Thesimple fact that the ice is there will help scientistconstrain models of impacts on the lunar surface and theeffects of meteorite gardening, photodissociation, and solarwind sputtering on the Moon. Beyond the scientificallyintriguing aspects, deposits of ice on the Moon would havemany practical aspects for future manned lunar exploration. There is no source of water on the Moon, and shipping waterto the Moon for use by humans would be extremely expensive($2,000 to $20,000 per kg). The lunar water could alsoserve as a source of oxygen, another vital material notreadily found on the Moon, and hydrogen, which could be usedas rocket fuel. Paul Spudis, one of the scientist who tookpart in the Clementine study, referred to the lunar icedeposits as possibly “the most valuable piece of real estatein the solar system”. It appears that in addition to thepermanently shadowed areas there are some higher areas suchas crater rims which are permanently exposed to sunlight andcould serve as a source of power for future missions.