InSight would use the reliable Mars Reconnaissance Orbiter, which has been at Mars since 2006, to relay data back home, whether or not the CubeSats made it - but WALL-E successfully sent back InSight data from each stage of the descent, as well as the lander's first image, while EVE was able to perform some radio measurements. Over 1,000 CubeSats have been launched.
All of this was achieved with experimental technology that cost a fraction of what most space missions do: $18.5 million provided by NASA's Jet Propulsion Laboratory in Pasadena, California, which built the CubeSats. One, nicknamed WALL-E, last contacted Earth Dec. 29, while the other, Eve, has been silent since January 4.
A number of the critical spare parts for each MarCO will be used in other CubeSat missions.
One important benefit of CubeSats is that each one carries its own navigation and communication systems.
NASA said that the pair will not begin moving toward the sun until this summer.
The mission team has several theories for why they haven't been able to contact the pair.
"This mission was always about pushing the limits of miniaturized technology and seeing just how far it could take us", said Andy Klesh, the mission's chief engineer at JPL, said in a statement. "We've put a stake in the ground". The mission could foretell a future of spacecraft bringing more CubeSats with them in the future.
After their work around Mars, the two spacecraft continued into deep space. "They were an excellent test of how CubeSats can serve as "tag-alongs" on future missions, giving engineers up-to-the-minute feedback during a landing".
The brightness sensors that allow the CubeSats to stay pointed at the Sun and recharge their batteries could be another factor. The satellites are still receding from the Sun, and their greater distance requires more precision in aiming their antennas toward Earth. The agency knows of a problem Wall-E has with a leaky thruster, and there's also doubt the two are capable of correctly pointing their antennas towards Earth as they go deeper into space.
While losing the MarCO spacecraft too early would be unfortunate, NASA said that they consider the mission a success.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science.
With over seven years of experience in online journalism, Vadim is passionate about everything related to science and the environment. Her writings have been published online in The Atlantic, Astronomy magazine's guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs.