Astronomy Picture of the Day
October 9, 2013

Isabella Crater and Surroundings
Isabella Crater and Surroundings

Credits: NASA/JPL - Magellan Project - Credits for the additional process. and color.: Dr Paolo C. Fienga/LXTT/IPF

Crater Isabella, with a diameter of approx. 175 Km (such as about 108,67 miles), as it is well seen in this NASA - Magellan Spacecraft Radar Image, is the second largest Impact Crater on Venus. Just out of curiosity, this impressive Impact Feature was so named in honor of the 15th Century Queen of Spain, Isabella de Castilla.

Located at approx. 30° South Latitude and 204° East Longitude, the Isabella Crater has two extensive Flow-like Structures extending to the South and to the South/East. The end of the Southern Flow partially surrounds a pre-existing and about 40 Km (approx. 24,84 miles) Circular Volcanic Shield. On the other hand, the South/Eastern Flow shows a complex pattern of Channels and Flow Lobes and it is overlain, at its South/Eastern tip, by (Rocky) Deposits possibly (better yet: most likely) coming from a later Impact Crater, whose diameter is about 20 Km (12,42 miles), and that was named Cohn (after Carola Cohn, an Australian Sculptor, born on April, 25th, 1892 at Bendigo and died on December, 23rd, 1964, at Phillip Island - both places located in the Australian State of Victoria).

These Extensive Flow-like Surface Features, which are unique to Venusian Impact Craters, are a continuing subject of study for a number of Planetary Scientists. According to one Theory, for instance, it has been thought that the Flows may consist of the so-called "Impact Melt", such as Rock that melted as a consequence of the extraordinarily intense heat that was released during the Impact Event. An alternate hypothesis, instead, invokes the idea of "Debris Flows"', which may consist of Clouds of Hot Gases and Solid Rock Fragments which raced all over and across the Venusian Landscape after the Impact Event had occurred. As a matter of fact, this second type of emplacement process is similar to that one which occurs during violent Volcanic Eruptions on our Home Planet Earth (such as, for instance, what happened in the AD 1991 during the Mount Pinatubo eruption - in the Philippines).

This frame (which is an Original NASA - Magellan Spacecraft Radio-Image published on the NASA - Planetary Photojournal with the n. PIA 00480), since it is just a Radio-Image of the Venusian Surface and NOT a real view of it, has been colorized, according to an educated guess carried out by Dr Paolo C. Fienga (LXTT-IPF), in what they could reasonably be its possible Absolute Natural Colors (such as the colors that a human eye would perceive if someone were onboard the NASA - Magellan Spacecraft and, once the thick layer of Venusian Clouds and Fogs is completely overcome, looked down, towards the Surface of Venus itself), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team.

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