Nasa's Maven spacecraft has arrived at Mars after a 442 million-mile journey that began nearly a year ago.
Nasa confirmed that the robotic explorer slipped into Martian orbit as planned.
Now the real work begins for the US$671m (€522.11 million) mission.
Flight controllers will spend the next six weeks adjusting Maven's altitude and checking its science instruments. Then Maven will start probing the Martian upper atmosphere.
The spacecraft will conduct its observations from orbit, and is not meant to land.
Scientists believe the Martian atmosphere holds clues as to how Earth's neighbour went from being warm and wet billions of years ago to cold and dry.
That early moist world may have harboured microbial life, a tantalising question yet to be answered.