Mars is getting another visitor or two.

This weekend, NASA's Maven spacecraft will reach the red planet following a 10-month journey spanning 442 million miles. If all goes well, the robotic explorer will hit the brakes and slip into Martian orbit Sunday night.

Maven is not designed to land. Rather, it will study Mars' upper atmosphere from orbit. Scientists want to learn how Mars went from a warm, wet world that may have harbored microbial life during its first billion years, to the cold, barren place of today. Maven should help explain the atmospheric changes that led to this radical climate change.

NASA launched Maven last November.

Hot on Maven's heels is India's first interplanetary spacecraft, which is due to go into orbit around Mars two days after Maven.