Over the last month, the Venus Express spacecraft has gently fallen through Venus's thick, carbon dioxide atmosphere, reaching a cloud-skimming altitude of 80 miles (130 kilometers).

For three weeks, the spacecraft will continue to fly low over the planet's sulfuric shroud, trying to sniff out any faint magnetic field that might be present, collecting information about the planet's clouds at these low altitudes and testing a technique that future robotic explorers might use. The maneuver, known as aerobraking, uses the planet's atmosphere to slow a spacecraft and adjust its orbit.

It isn't meant to be the final plunge for Venus Express. But it could be, depending on how the spacecraft fares and how much fuel is