“Rummaging through Earth’s Attic for Remains of Ancient Life”

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

Period of Heavy Bombardment - Frequent impacts

Period of Heavy Bombardment

- material ejected over range of velocities

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





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

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“Rummaging through Earth’s Attic for Remains of Ancient Life”