Immature lunar formations and palaeoregolith deposits as sources of information about

history of the Solar System

Sinitsyn M.P. Lunar and planetary investigations division

Sternberg Astronomical InstituteMoscow State University

Tree types of radiations(SW,SCR,GCR) affecting the surface of the Moon

SW SCR GCR- Energy of the nucleons 0.3-3 kev/u 1-100Mev/u 0.1-10Gev/u

- Proton flux 3*10E8 0-1*E6 2-4 (1/cm**2sek)

- ratio of the protons/alpha particles ~22 ~60 ~7

- penetration depth of protons and alpha part. ~micron centimeters meters heavy nuclides ~micron millimeters centimeters

- composition (%): protons ~ 85-90 % alpha ~ 10 % more heavy ~ 1 %

A typical shock formation structure

Immature impact melt as a possible source of information about the last 200 million years of lunar history

• fresh impact in Oceanus Procellarum. At the bottom of the crater can be seen impact melt.

• Farside fresh impact. Visible jet of the melt on the slopes and close to the edge of the crater.

(Images produced by LROC)

Impact melt on the slope and at the edge of crater rim (slope and horizontal)

Impact melt of the Giordano Bruno fresh crater about 6 km away from edge (horizontal surface)

(images of LROC)

Impact melt at the edge of the immature craters

Some impact melts

• Impact melts on the Ticho crater floor .

• Blocked impact melt on the Giordano Bruno crater floor. It is possible to obtain a vertical column of this melt without drilling

(LROC Images)

Increased hydrogen concentration of some immature(fresh) impact craters by Lunar Prospector Neutron Spectrometer

results

Crater Proclus, 20-40 mil. yrs Crater Aristarchus, ~60 mil. yrs Crater Timocharis, ~80 mil. yrs

The hydrogen content in marine formations of the Moon according to the LPNS

LROC image and hydrogen distribution on the Mare Nectaris neighborhood

Crater Cleomed (with the seabed) and the north coast of Mare Crisium

HighlandMare Crisium

Hydrogen distribution on the border of highland and Mare Crisium

Some additional features of the distribution of hydrogen

Distribution of hydrogen in the Caucasus mountains

Hydrogen anomaly in the vicinity of Fra- Mauro (~ 200 ppm)

Distribution of hydrogen in the Appeniny mountains

The vertical column of the lunar regolith, delivered by Apollo-12 spacecraft

• digging depth of 3 meters• this depth corresponds to 3

billion years of lunar history...

• ...but, regolith is considerably mixed

• there is a large number of tracks

• Is it possible to detect not mixed regolith?

Palaeoregolith• Any regolith, located between the two lava flows at a

depth of 3 meters can be considered closed to cosmic radiation

• Traces of Cosmic Rays in palaeoregolite have very precise information relating to a specific time period.

• One of the possible problems of the LROC is to determine the locations of places of occurrence of palaeoregolith layers.

Palaeoregolith on Bessel crater’ slope

• Creter Bessel

Mare Serenitatis,

Diameter 16 km

Depth 1,7 km.

• Location basalt layers one above the other on the wall of Bessel crater. The palaeoregolith layers are clearly visible between the layers of basalt.

(LROC Images)

Palaeoregolith on Euler crater’ slope

• Creter Euler

Mare Imbrium,

Diameter 28 km

Depth 2.2 km.

• The palaeoregolith between basalt layer on the slope of Euler crater.

(LROC Images)

Possible source of palaeoregolith on terraces of Necho and Burg craters

• Necho crater with terraces

Mare Imbrium,

Diameter 30 km

Depth 2.1 km.

• Possible source of palaeoregolith on terraces of Burg crater (d=40 km. depth =1.8 km)

(LROC Images)

• As a result of tectonic forces generated any breaks the surface (faults).

• Some faults can expose deposits of palaeoregolith.

Tectonic and volcanic extended objects are Possible source of palaeoregolith

• Formation preserved regolith under new volcanic lava.

The volcanic lava of resent volcano of Tsiolkovsky crater.

• Formation preserved regolith under impact melt flow on edges of any craters rims.

New formation of modern palaeoregolith (preserved regolith) layers.

• Concentration of volatile isotopes (H,He,Ar,Ne,Xe,N) in the lunar regolith make it possible to trace the changes of the solar wind for up to 4 billion years.

• There are serious reasons to believe that the ancient solar wind flow was 2-3 times higher. This is indicated by the steady increase in the ratio of nitrogen isotopes .

• Changes in the depth of penetration of solar wind to the minerals give the opportunity to explore the change of energy of solar wind protons.

• Studies of galactic cosmic rays for a period of up to 4 billion years, will provide an opportunity to reconstruct the history of motion of solar system around the galactic center (the periods of passage through galactic arms).

• Studies of galactic cosmic rays over the period to 200 million years will provide an opportunity to reconstruct the history of galactic events around the Solar System (eg supernova explosions).

• Correlation of galactic events with periods of evolution of life.

Potential information about Solar System history that possible to obtain from an impact melt and palaeoregolith

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Summary