Phobos is not a slowpoke. Given its size, angle and orbital pattern, the moon makes a full circle around Mars approximately every 7.6 hours. This frequency also makes it much more likely to pass in front of the sun than solar eclipses on Earth. If you were hypothetically in the right location at the right time on Mars, you might catch a glimpse of the small, potato-shaped satellite that briefly turned the sun into a giant Google eye. NASA’s Mars Perseverance rover captured just such an event in February, and managed to photograph another eclipse just seven months later.
NASA recently exhibited the last Phobos eclipse seen on September 30 from the rover’s vantage point on Mars’ Jezero crater. Once again, the Google Eye’s lifetime lasted just shy of 30 seconds, making the minute-long eclipse events on Earth seem long by comparison. Like the latest documentation, the images of Phobos were captured using Perseverance’s Mastcam-Z, an instrument co-designed and supervised by Arizona State University.
Astronomer Asaph Hall discovered the two moons of Mars in 1877, naming them Phobos and Deimos after the two Greek gods of fear and anxiety. Although their origins are still unclear, experts theorize that the pair originated as asteroids captured by Mars’ gravity, or as debris left over from the formation of the solar system.
[Related: A Martian solar eclipse turns the sun into a giant googly eye.]
At just 17 miles (28 kilometers) wide, Phobos is about 157 times smaller than Earth’s moon, although both travel slowly in opposite directions. While the moon is currently moving away from Earth at a rate of about 1.5 inches per year, both Phobos and Deimos are moving closer to Mars by an estimated 6 feet per century. At that rate, the moons are predicted to collide with their host planet in about 50 million years, or break into countless smaller pieces to form a Saturn-like ring.
Until then, though, there will be many more Google-eye opportunities for Perseverance – and perhaps someday human visitors – to document.