Mars 2020 encapsulation
NASA's Mars 2020 spacecraft (center) shortly before the spacecraft was encapsulated within the Atlas 5 payload fairing in June. NASA/Christian Mangano

WASHINGTON — The launch of NASA’s next Mars rover mission has been delayed to no earlier than July 30 because of a launch vehicle processing issue, the latest in a series of slips that have now used up nearly half of the available launch opportunities for the mission.

NASA announced June 30 that the mission, previously scheduled to launch July 22, would be delayed to investigate “off-nominal” data from a liquid oxygen sensor line during a wet dress rehearsal of the mission’s Atlas 5 launch vehicle June 22 at Cape Canaveral, Florida.

During the wet dress rehearsal, the Atlas 5 rocket, without the Mars 2020 spacecraft attached, is rolled out to the pad and loaded with propellants. Controllers go through the countdown until just before T-0 to test the vehicle’s systems. After the test, the rocket’s liquid oxygen and liquid hydrogen tanks are drained and the vehicle returned to its integration building.

The mission was originally scheduled to launch July 17, the beginning of its launch period, but has slipped three times. None of the slips have had to do with issues with the Mars 2020 spacecraft itself. A problem with a crane using in launch vehicle processing caused a three-day delay, NASA announced June 10. Two weeks later, the agency said “a contamination concern in the ground support lines” in a payload processing facility would push the launch back two additional days, to July 22.

NASA previously stated that the launch period for Mars 2020 would close on Aug. 11. However, NASA said during a pre-launch briefing about the mission June 17 that the period could be extended to Aug. 15. NASA confirmed in the latest launch delay announcement that the mission can now launch as late as Aug. 15.

The agency added that it is “examining if the launch period may be extended further into August.” Any additional days that could be added beyond Aug. 15 likely will have far shorter windows each day than the two-hour window available for a July 30 launch.

After the initial three-day delay, NASA officials said they were confident the mission would still lift off before the launch period closes. “We think we have some robustness there, some good robustness there, in the launch window,” Matt Wallace, deputy project manager for Mars 2020, said at the June 17 briefing.

If Mars 2020 did not lift off before the launch period closed, NASA would have to wait until the next launch opportunity in 26 months. The cost of that delay, previously stated by NASA Administrator Jim Bridenstine to be as much as $500 million, was a major reason why the agency made Mars 2020 one of its highest priorities, alongside the SpaceX Demo-2 commercial crew mission, during the coronavirus pandemic.

Mars 2020, carrying a rover named Perseverance, will land on Mars on Feb. 18, 2021, regardless of what day it launches during the current launch period. The rover will land in Jezero Crater on Mars for mission designed to last at least one Martian year, or 687 Earth days.

Perseverance’s instruments will look for signs of past life on Mars, but the mission’s biggest purpose is to cache samples of Martian rock for later return to Earth. Mars 2020 is the beginning of a Mars Sample Return campaign that will feature two missions launching in 2026 to collect the samples, launch them into Martian orbit and return them to Earth. NASA will work with ESA on those two missions.

Those two missions are still in the early phases of planning, but NASA expects they’ll be ready for a 2026 launch provided Perseverance makes it to Mars. “We are right now working towards a goal of being ready to launch in 2026 the remaining two legs of sample return to go collect those samples and bring them back to Earth for a landing in 2031,” Jim Watzin, director of NASA’s Mars Exploration Program, said during a June 24 SpaceNews webinar about the mission.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...