Doomsday for NASA craft: Messenger plunges into Mercury

NASA's Messenger spacecraft has crashed into the planet Mercury after running out of fuel, in an incident expected by the U.S. space agency.

On Thursday, Messenger — which stands for Mercury Surface, Space Environment, Geochemistry, and Ranging — slipped out of orbit following a successful four-year tour of the rocky planet.

NASA said it was powerless to stop gravity from dragging the spacecraft towards the planet.

Its collision at a speed of more than 8,600 mph added another small crater to Mercury's already pitted surface.

Messenger became the first spacecraft to orbit hot, little Mercury, in 2011. Since then, it's circled the solar system's innermost planet 4,104 times and collected more than 270,000 images.

Flight controllers managed to keep the spacecraft going in recent weeks by using helium gas not originally intended as fuel. But now the gas is gone and gravity is tugging.

Mercury is the last of the rocky inner planets in our solar system, which counts Mars and Venus, to be littered by humans.

"I want to send out a big thank you to everyone who has worked on my mission and has followed my story!!" the Messenger team said via Twitter on Thursday morning. This tweet followed a few hours later, along with a sad face emoticon: "Well, I've got 3 hours and 26 minutes left."

Messenger was launched from Cape Canaveral, Florida, in 2004.

Al Jazeera and The Associated Press