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“Rummaging through Earth’s Attic for Remains of Ancient Life”. John C. Armstrong, Llyd E. Wells, Guillermo Gonzalez Icarus 2002, vol. 160 December 9, 2004 Ashley Zauderer. What was the Ancient-Earth like?. Images courtesy of NASA. When did the moon form?. Images courtesy of NASA. - PowerPoint PPT Presentation
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Rummaging through Earths Attic for Remains of Ancient LifeJohn C. Armstrong, Llyd E. Wells, Guillermo GonzalezIcarus 2002, vol. 160
December 9, 2004Ashley Zauderer
What was the Ancient-Earth like?Images courtesy of NASA
When did the moon form?Images courtesy of NASA
When did life develop?Images courtesy of NASA
Could early remains from the Earth be buried in the Moons regolith in high enough concentrations to motivate a search mission?
Images courtesy of NASA
BackgroundEarliest geologic information we have about the Earth dates back to 3.476 Gyr
Goal: How and when did life develop on the Earth?
Preservation on the Moon?
No atmosphereNo widespread, long-lived volcanismLacks hydrologic & tectonic cyclesImages courtesy of NASA
ProcedureCalculate mass of material incident on Earth during period of interest
Determine velocity distribution of material ejected from Earth during impacts
Apply transfer efficiencies to estimate the mass reaching the moon
Determine the fractional volume of terran material in lunar regolith compared to total material accreted from other sources
Lunar Timeline
Large Craters in North AmericaEarth Impact Database Planetary and Space Science Center
ProcedureCalculate mass of material incident on Earth during period of interest
Determine velocity distribution of material ejected from Earth during impacts
Apply transfer efficiencies to estimate the mass reaching the moon
Determine the fractional volume of terran material in lunar regolith compared to total material accreted from other sources
Period of Heavy Bombardment - Frequent impacts
Period of Heavy Bombardment
- material ejected over range of velocities
ProcedureCalculate mass of material incident on Earth during period of interest
Determine velocity distribution of material ejected from Earth during impacts
Apply transfer efficiencies to estimate the mass reaching the moon
Determine the fractional volume of terran material in lunar regolith compared to total material accreted from other sources
Ejecta Transfer ProcessesDirect Transferv ~ escape velocityOrbital Transferv = escape velocityLuckyv >> escape velocity
Direct TransferLow relative velocity with respect to the moongravitational focusingMaximum velocity ~ escape (11.2 km/s) Minimum velocity ~ 10.94 km/sZharkov (2000) estimates at 3.9 GyrMoon was ~ 21.6 earth radii awayPeriod ~ 5.9 days
Orbital TransferVelocity ranges: 11.2 11.7 km/sNumerical simulations by Stadel (2001) using the pkdgrav code with variable timesteps, N = 252 ejecta particles and planetsConservative estimate since they only determined material transferred in 5000 years or less
Las Vegas TransferFor particle velocities > escape velocity
Depends on cross-sectional area of the moon at given time
ProcedureCalculate mass of material incident on Earth during period of interest
Determine velocity distribution of material ejected from Earth during impacts
Apply transfer efficiencies to estimate the mass reaching the moon
Determine the fractional volume of terran material in lunar regolith compared to total material accreted from other sources
ProcedureCalculate mass of material incident on Earth during period of interest
Determine velocity distribution of material ejected from Earth during impacts
Apply transfer efficiencies to estimate the mass reaching the moon
Determine the fractional volume of terran material in lunar regolith compared to total material accreted from other sources
Finally, estimate the likelihood of survival of the biological and geochemical tracers.
Survivability of tracersas a function of velocityArmstrong et al., Icarus 2002
Conclusions-surface abundance of terran material on the moon estimated to be 7 ppm(20,000 kg over a 10 km x10 km region)
1-30 kg transferred from Venus>180 kg tranferred from MarsImages courtesy of NASA
EarthEarth
References-Armstrong, John C., Wells, Llyd E. and Gonzalez, Guillermo. Icarus 160, 183-196 (2002).
-Melosh,H. 1985. Ejection of rock fragments from planetary bodies. Geology 13, 144-148.
-Zharkov, V.N. 2000. On the history of the lunar orbit. Solar System Res. 34, 1-11.
Images courtesy of NASA