Venus Mars Earths Moon S Pole Mercury Mistastan Slides: 37 Download presentation Venus Mars Earth’s Moon (S. Pole) Mercury Mistastan Lake, New Foundland, Canada 28 Km 38, 000 years Barringer Meteor Crater, AZ 1. 18 km 49, 000 years Wolf Creek, Australia 0. 875 Km 300, 000 years Bosumtwi, Nigeria 10. 5 Km 1. 3 Million years Roter, South Africa 2. 5 km 5 Million years Karakul, Tadjikistan 45 Km < 10 Ma Chicxulub, Mex 170 Km 65 Ma Deep Bay, Sask. 13 km Clearwater Lakes, Sask. 32 km/22 km 290 Million years 100 Million years Gosses Bluss, Australia 22 km 142. 5 Million years Aorounga, Chad 17 km 200 Million years Manicougan Lake, Quebec 100 km 212 Million years Radar Image of NEO 1999 JM 8 Missed Earth by 5 million km in 1990, 6 million km in 1999 Average diameter 3. 5 km Tunguska Event, 1908, Russia 80 million trees knocked down over 2, 150 square kilometres (830 square miles Tunguska Event 1908 Equivalent to a 100 MT Nuclear Bomb Blast Question If cratering rate on Earth is same as our Moon, why are their so few craters preserved? What is wrong here? Apollo 14 site spherules (~ 0. 2 mm diameter) Argon 40/Argon 39 dates (accuracy ~ +/- 200 MY) Apollo 14 site spherules (~ 200 micro-meters diameter) Argon 40/Argon 39 dates (accuracy ~ +/- 200 MY) => 26 Ma periodicity 1 BY averaging bins Black and opaque spherules only Question: If cratering rate on Earth is same as our Moon, why are their so few craters preserved? Answer: Erosion