Compared to Mercury, the Moon and other such bodies, Venus has very few craters. In part, this is because Venus's dense atmosphere burns up smaller meteorites before they hit the surface. The "Venera" and "Magellan" data are in agreement: there are very few impact craters with a diameter less than , and data from "Magellan" show an absence of any craters less than in diameter. The small craters are irregular and appear in groups, thus pointing to the deceleration and the breakup of impactors. However, there are also fewer of the large craters, and those appear relatively young; they are rarely filled with lava, showing that they were formed after volcanic activity in the area ceased, and radar data indicates that they are rough and have not had time to be eroded down.