1) Impact crater on Mars 
Vishniac (Вишняк) could refer to: ...[crater] Vishniac is a largest crater of the Martian surface feature called the Giant`s Footprint. It was named after Wolf V. Vishniac, a microbiologist who died on an expedition to Antarctica. Fittingly, the crater lies in the Antarctic of Mars. The feature was originally observed by Mariner 7 in 1969. In 1999, the Mars Global Surveyor`s M...