WASHINGTON — The first-ever interplanetary cubesats went dark just before their big moment last fall, spurring a last-minute rescue effort. The two satellites, part of NASA's $18 million MarCO (Mars Cube One), mission were tasked primarily with demonstrating that tiny spacecraft can explore deep space. But team members also wanted the spacecraft to help relay communications from NASA's InSight Mars lander during the latter's touchdown attempt on Nov. 26, 2018. Just a day before the landing, however, MarCO-B, "suddenly did not appear" during the remote check-in with engineers at NASA's Jet Propulsion Laboratory (JPL), mission chief-engineer Andrew Klesh said during a presentation at the International Astronautical Congress here on Friday (Oct. 25).