Compton-Belkovich thorium anomaly

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Volcanic hotspot on the moon
Compton-Belkovich thorium anomaly
Position of the Compton-Belkovich thorium anomaly on the Moon.
Position of the Compton-Belkovich thorium anomaly on the Moon.
Compton-Belkovich Thorium Anomaly (Moon North Pole Region)
Compton-Belkovich thorium anomaly
position 61 ° 6 ′  N , 99 ° 30 ′  E Coordinates: 61 ° 6 ′ 0 ″  N , 99 ° 30 ′ 0 ″  E
surface 576 km²dep1
history
Named after nearby craters

The Compton-Belkovich Thorium Anomaly is a hotspot ( volcanic complex) on the far side of the moon. It was discovered in 1998 with the help of the Lunar Prospector . In this region there is a high concentration of the weakly radioactive element thorium . Based on the rock samples from the Apollo missions , it was previously assumed that volcanism on the moon had reached its peak three to four billion years ago. These results now point to significantly more recent volcanic activities about a billion years ago on the back of the moon.

description

The Compton-Belkovich Thorium Anomaly was recorded in 1998 by the gamma-ray spectrometer on board the Lunar Prospector and subsequently recognized as a volcanic hotpot. The calculated thorium concentration reaches 5.3 micrograms per gram, while the basalt in the surrounding highlands only contains between 0 and 2 µg / g. Compared to the ratios on earth of 0.06 µg / g it is very high in the Compton-Belkovich anomaly. In addition, it has a very high reflectance , as shown by an imaging study that was later carried out with the help of the Clementine probe . High-resolution images from the Lunar Reconnaissance Orbiter enabled a more detailed analysis of the surface properties of the Compton-Belkovich thorium anomaly in 2011.

location

The anomaly is located between the Belkovich crater , which is 214 km in diameter, and the Comptom crater (162 km in diameter). The region itself is 32 km wide and 18 km long.At the center of the region is a volcanic complex with a Extension of 25 km by 35 km. It is located approx. 900 km from the northeastern Procellarum-KREEP-Terrain , in which a high occurrence of the rock component KREEP has been determined.

properties

At the center of the elevated region is a depression surrounded by steep slopes that could be a crater . To the north there is a structure with a diameter of 500 meters called the "Small Dome". Further north is an elongated dome that has a north-south orientation and is called the "Middle Dome". It is 2.5 km long and 600 meters wide. Both the "Small Dome" and the "Middle Dome" have boulders on the summit that could be of volcanic origin. At the northern edge of the anomaly is what is known as the "Great Dome". It has a diameter of 2.5 km and a dent at the summit.

An offshoot of the reflective substance extends to the southeast from the hill of about 7 km. It is believed that it could be the remains of a pyroclastic flow . This highly reflective surface matches a surface that shows a Christiansen effect with a shorter wavelength - it reflects more strongly in the range from 7.1 to 7.5 μm, which suggests a main component of quartz or alkali feldspars .

Remnants of the explosion are also scattered over 300 km in the eastern part and are found in an area of ​​70,000 km².

Volcanic slope

Volcanic properties provide information about the composition of the lava found in the Compton-Belkovich thorium anomaly. On average, most of the volcanoes on the Moon have slopes that slope less than 7 degrees. This area, on the other hand, has a slope of up to 25 degrees. This suggests that the region was formed by liquid lava.

composition

Based on the data that the Clementine probe delivers in an infrared spectrum of 750 nm and 950 nm, the proportion of iron oxides is approx. 3% of the mass.

formation

The analysis of the rock samples from the Apollo program has shown volcanic activity in the period from three to four billion years ago, with these samples coming exclusively from the earth-facing side of the moon . On the other hand, volcanism seems to have occurred on the back of the moon a billion years ago. The uniform surface in the area of ​​the anomaly suggests that it was formed in a much more recent eruption.

When the lava cooled, a crystallization process took place in which silicate structures were formed. Incompatible elements such as thorium have accumulated in the remaining liquid rock. The eruption associated with the thorium anomaly may have created the ridges to the west and the low, wide plain to the east. The latest lava eruptions have probably left the domes with the steeper slopes and also formed small bulges in places where they barely reached the surface.

Web links

Individual evidence

  1. ↑ a b c d e B. L. Jolliff, TN Tran, SJ Lawrence, MS Robinson: Compton-Belkovich: Nonmare, Silicic Volcanism on the Moon's Far Side . In: 42nd Lunar and Planetary Science Conference . 2011 ( usra.edu [PDF; accessed on May 14, 2012]).
  2. ↑ a b c D. J. Lawrence, RC Elphic, WC Feldman, O. Gasnault, I. Genetay, S. Maurice, TH Prettyman: Small-Area Thorium Enhancements on the Lunar Surface . In: Harvard University (Ed.): 33rd Annual Lunar and Planetary Science Conference . March 2002, bibcode : 2002LPI .... 33.1970L .
  3. ↑ a b c B. L. Jolliff, SA Wiseman, SJ Lawrence, TN Tran: Scientific Return from Systematic Imaging of the Constellation Exploration Sites: Compton – Belkovich Example . In: Harvard University (Ed.): 41st Lunar and Planetary Science Conference . March 2010, bibcode : 2010LPI .... 41.2412J .
  4. ^ A b D. J. Lawrence, RC Elphic, WC Feldman, TH Prettyman, O. Gasnault, S. Maurice: Small-area thorium features on the lunar surface . In: Journal of Geophysical Research . 108, 2003, p. 5102. bibcode : 2003JGRE..108.5102L . doi : 10.1029 / 2003JE002050 .
  5. ↑ a b c d Bradley L. Jolliff, Sandra A. Wiseman, Samuel J. Lawrence, Thanh N. Tran, Mark S. Robinson, Hiroyuki Sato, B. Ray Hawke, Frank Scholten, Jürgen Oberst, Harald Hiesinger, Carolyn H. van der Bogert, Benjamin T. Greenhagen, Timothy D. Glotch and David A. Paige: Non-mare silicic volcanism on the lunar farside at Compton – Belkovich . In: Nature Geoscience . 4, No. 8, July 24, 2010, p. 566. doi : 10.1038 / ngeo1212 .
  6. ↑ a b Rare Volcanoes Discovered On Far Side of the Moon . In: Space.com , July 25, 2011. Retrieved May 10, 2012. 
  7. ↑ a b Unique volcanic complex on the far side of the moon . In: WUSTL (Education - Edu) - News . July 24, 2011. Retrieved March 7, 2012.
  8. ↑ Durham University: Extent of Moon's giant volcanic eruption is revealed . PhysOrg. March 18, 2015. Accessed March 19, 2015.
  9. ↑ JJGillis, BL Jolliff, DJ Lawrence, SL Lawson, TH Prettyman: The Compton-Belkovich Region of the Moon: Remotely Sensed Observations and Lunar Sample Association . In: 33rd Lunar and Planetary Science . 2002 ( usra.edu [PDF; accessed on May 14, 2012]).
  10. ↑ DJ Lawrence, WC Feldman, BL Barraclough, AB Binder, RC Elphic, S. Maurice, MC Miller, TH Prettyman: Thorium abundances on the lunar surface . In: Journal of Geophysical Research . 105, No. E8, 2000, pp. 20, 307-320, 331. bibcode : 2000JGR ... 10520307L . doi : 10.1029 / 1999JE001177 .
  11. ^ Paul H. Warren: Compositional structure within the lunar crust as constrained by Lunar Prospector thorium data . In: Geophysical Research Letters . 28, No. 13, 2001, pp. 2565-2568. bibcode : 2001GeoRL..28.2565W . doi : 10.1029 / 2000GL012739 .
  12. ↑ Bradley L. Jolliff, Sandra A. Wiseman, Samuel J. Lawrence, Thanh N. Tran, Mark S. Robinson: Non-mare silicic volcanism on the lunar farside at Compton – Belkovich . In: Nature Geoscience . tape 4 , no. 8 , p. 566-571 , doi : 10.1038 / ngeo1212 .