A Mars scientist shares the inside story of the NASA Curiosity rover's poignant first photo of Earth and Mars moon Phobos together in the twilight sky.

When approaching Earth, asteroids tend to do one of two things: Most of the time, they miss. Sometimes, they hit, leaving a bright streak in our planet’s sky or a gruesome new wound in its crust. But very rarely, asteroids are captured by Earth’s gravity and pirouette around the planet, becoming, in effect, a moon — albeit an ephemeral one.

NASA's Curiosity rover has captured a spectacular sight from the surface of Mars: The first-ever photo of Earth alongside the Red Planet's moon Phobos.

It is the first time ever the two have been captured together from the surface of Mars. NASA's Curiosity Mars rover used its Mast Camera, or Mastcam, to capture the view of Earth setting while Phobos is rising.

In an out-of-this-world first, Earth and Phobos have been photographed together in the sky by NASA’s Curiosity. The rover has previously snapped this moon and its companion Deimos, including in a beautiful eclipse,