The twin landers, each the size of a desk and weighing 375 pounds (170 kilograms), will ramble dozens of meters a day, drilling into rocks and scooping up soil in preliminary field studies to help identify ancient oases.

CNN: Race to Mars begins a distant search for life

Venus is a twin to the Earth in terms of size and mass, yet has evolved in a very different direction, with a surface temperature hotter than a kitchen oven and a choking mixture of noxious gases for an atmosphere.

BBC: Venus mission is on

Mourners streamed into the newly opened memorial, which has two reflecting pools, each almost an acre in size, in the footprints of the twin towers.

BBC: 9/11 anniversary: Sombre US honours victims 10 years on