How can we study quakes on other planets?

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How can we study quakes on other planets?

• Cannot do it entirely from earth
• Need to send people or landers to the planet

On the Moon
Apollo Mission sent astronauts to the moon
1969-1972 where they installed 6 seismometers (4
were operational) on the near side. Stations
returned data through 1977 (8 yrs) Recorded
between 600-3000 moonquakes per year
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Lunar Seismic Events

• More than 12,000 quakes recorded (between M
  0.5-1.5)
• Three types of events were recorded

• meteor impacts (pea size impacts up to 1000 km
  away)
• Astronaut noise (landings and rocket boosts, and
  even foot
• steps)
• moonquakes
• some shallow events lt 60 km deep
• mostly deep focus
• deep events form a partial spherical shell
  between 600-1,000 km depth

Near side
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Shallow lunar structure from seismology
Both P and S velocities increase regularly with
depth. Inferred density shows that a material
with r3 exists to 60 km consistent with basalt
and gabbro (crust) Deeper than 60 km assumed
density is consistent with pyroxenes (mantle)
crust
mantle
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Moonquakes
With no active tectonics or volcanism, what is
causing the moonquakes, and why are they so deep?

• Something must be causing applied stresses
• Possibly thermal stress from cooling
• more likely tidal stresses from the Earth (6x
  greater than on earth)
• Why are the quakes only on the near side?
• Similar tidal stresses exist on back side
• quakes probably exist on backside too but not
  easily detected (size, distance)

?
5
Seismicity on other planetoids

• Mars 1970s Viking I II landers were equipped
  with seismometers.
• Though there are no active tectonics, Mars is
  expected to have considerable thermal stress
  (actively cooling) and is thought to be more
  active than the moon.
• Seismometer on Viking
• I did not work
• II worked for 2years but only recorded
• 1 marsquake
• poorly coupled to surface
• significant wind noise
• considerable temperature
• variations
• Seismometers have not been deployed to any other
  planetary object

What planetoids would be good candidates for
future seismic studies?
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What planetoids would be good candidates for
future seismic studies?

• body should be composed of brittle elastic solids
  for quakes (no gas giants Jupiter, Saturn,
  Uranus, Neptune)
• must be accessible with a lander and return data
  (stay within the solar system)
• Must have induced stresses (tidal, thermal,
  cratering)

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What planetoids would be good candidates for
future seismic studies?

• Great candidates include
• Venus
• possible volcanism (quakes associated)
• thick atmosphere tough to penetrate!

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What planetoids would be good candidates for
future seismic studies?

• Great candidates include
• Venus
• possible volcanism (quakes associated)
• thick atmosphere tough to penetrate!
• Galilean Moons
• Io most active body in solar system

9
What planetoids would be good candidates for
future seismic studies?

• Great candidates include
• Venus
• possible volcanism (quakes associated)
• thick atmosphere tough to penetrate!
• Galilean Moons
• Io most active body in solar system
• Europa Ice tectonics

10
What planetoids would be good candidates for
future seismic studies?

• Great candidates include
• Venus
• possible volcanism (quakes associated)
• thick atmosphere tough to penetrate!
• Galilean Moons
• Io most active body in solar system
• Europa Ice tectonics
• Callisto Cratering
• Almost any large rocky
• body would work