Geology of the Moon, Mercury, and Mars

How the maria formed A very large impact fractures the crust and creates ringed mountains Structure is called an “impact basin” Low viscosity lava flows up through the cracks and fills the basin This happened after the period of late heavy bombardment, so there are relatively few craters in the maria

Mare Orientale is a textbook example of an impact basin Very little lava flooded Orientale because it happened late – it was probably the last large impact basin to form. (Compare to Mare Imbrium) Ringed mountains Flat mare (few craters) Mare Orientale

Interestingly, the far side of the Moon has no large maria The near-side has many large maria The crust is thicker on the far side, and so impacts are much less likely to fracture it down to molten material But why is it thicker there? We don’t know.

The Moon also has interesting features called “rilles” They’re all over, but we’re going to visit one here

This is “Hadley Rille” Mount Hadley Apollo 15 landing site

Here the Apollo 15 lunar rover is parked next to Hadley Rille 1200 ft deep in this area, ~ 80 miles long “Sinuous Rilles” are lava tubes that ran dry and collapsed, leaving a winding valley

On which side of the Moon is the crust the thickest? A) The far side B) The near side C) They are equally thick D) We have no way of knowing

On which side of the Moon are maria more prevalent? A) The far side B) The near side C) They are equally prevalent on both sides

The surface of the Moon is covered by loose, powdery material called regolith. It is the product of constant bombardment from micrometeorites. It has very different properties from the “soil” of Earth: Very dry and sharp edged Electrostatically charged, so it clings to everything

2 – 4 mm sample of lunar regolith NOTE the glass spherules

Microscopic regolith sample Note the sharp edges

Astronauts inside the lunar lander after an EVA were coated with it Gene Cernan, Apollo 17 This stuff gets into everything, and raises serious technical problems!

Mercury shows similar features, though no large maria Notice that in many areas, like this one, the impact craters are not as closely packed as in the lunar highlands But more so than in the lunar maria. This suggests that this area was covered by lava flows late in the heavy bombardment era

Lobate scarps on Mercury This is a form of tectonics we do not see on any other terrestrial planet

Rank these surfaces from oldest to youngest: B) 1, 3, 2 C) 2, 3, 1 D) 2, 1, 3 E) 3, 2, 1 1 3 2

Percival Lowell and Mars 1879 Giovanni Schiaparelli reported linear features on Mars He called them “canali”, Italian for “channels” 1895 Percival Lowell published maps of “canals” on Mars 1898 H. G. Wells War of the Worlds (Radio broadcast was 1938, Oct. 30) 1950 Ray Bradbury The Martian Chronicles 1965 NASA’s Mariner 4 spacecraft: No Martians

A current map of Mars Volcanism Tectonics

Valles Marineris

~85,000’ 29,029’ 33,500’

Evidence of water on Mars 1

Evidence of water on Mars 2 Mars rovers have found many examples of minerals that are known to form only in the presence of liquid water

Evidence of water on Mars 3 Here gypsum fills a crack in Martian rock. The gypsum was deposited by water flowing through the cracks in the rock.

Evidence of water on Mars … Evidence of recent (last million years or so) water erosion on a crater wall

Evidence that liquid water occasionally flows on today’s Mars Released in summer 2015… Evidence that liquid water occasionally flows on today’s Mars (just below the surface)

Recurring Slope Lineae (RSL) They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons. Scientists discovered hydrated salts in these lines. On Earth these salts are known to lower the freezing point of liquids to as low as -94º F The RSL are “likely a shallow subsurface flow, with enough water wicking to the surface to explain the darkening.”

Astro-Cash Cab! Jesse K. Emily Amanuel JC Katy

1) Matching: A) Regolith _____ B) Impact basin _____ C) Sinuous rille _____ 1) Collapsed lava tube 2) A large, ringed area indicating a very large impact event 3) Loose, powdery material on the lunar surface

2) Put these 3 things in age order, from youngest to oldest: The mare The crater The rille

3) What is this feature on the surface of Mercury called?

4) On which planet will you find the largest volcano in the solar system?