Which NASA orbiter discovered recurring slope lineae, dark seasonal streaks on Mars?

NASA’s Mars Reconnaissance Orbiter discovered recurring slope lineae, dark seasonal streaks on Mars.

Researchers using the orbiter’s High Resolution Imaging Science Experiment, or HiRISE, identified recurring slope lineae in images published in 2011. These narrow features appear on steep, warm-season slopes and fade during colder periods, suggesting a seasonal process.

They were initially considered possible evidence of flowing liquid water. Later research found that dry granular flows, in which dust or sand moves downhill, can explain many observations. Hydrated salts were detected at some sites, but the exact role of water remains an active subject of study.

Recurring slope lineae are not permanent rivers and should not be confused with ancient valley networks carved billions of years ago. Mars Reconnaissance Orbiter reached Mars in 2006 and continues to provide exceptionally detailed images and measurements of the planet’s surface and atmosphere.