WASHINGTON — Development of a NASA mission to collect samples on Mars for later return to Earth has suffered a setback, although one that project officials said should not affect its 2020 launch date.

In a statement released late April 26, NASA’s Jet Propulsion Laboratory said a structure that is part of the heat shield for the Mars 2020 spacecraft cracked during testing earlier in the month at a Lockheed Martin facility near Denver.

The fracture in the composite structure is located near the outer edge of the shield and spans its circumference, according to the JPL statement. It was detected April 12 after the heat shield underwent a week of testing at the Lockheed facility where it was subjected to forces 20 percent above those expected in a normal entry into the Martian atmosphere.

Mars 2020 project officials at JPL are working with Lockheed Martin to determine the cause of the cracking. JPL said the structure will be repaired to support other spacecraft testing, but will not be flown. A new heat shield will be built for use on the mission.

The heat shield that cracked was one of two built more than a decade ago for the Mars Science Laboratory (MSL) mission, which landed the Curiosity rover on the surface of Mars in August 2012. The shield underwent testing in 2008 and was as a spare for the one used on the MSL mission.

Mars 2020 is based on the MSL design, using the same approach for entry, descent and landing that was successful for that earlier mission. Mars 2020 makes use of spare hardware from MSL but with some changes, such as more durable wheels on its rover and a different suite of instruments.

JPL didn’t disclose the cost of repairing the damaged heat shield structure and building a replacement. It did state that it should have no effect on the mission’s planned July 2020 launch.

Mars 2020 is intended to be the first phase of a multi-mission effort to return samples of Martian rock and soil to the Earth. The rover will cache those samples in containers, which will be collected by a later mission that will then launch them into Martian orbit. Another spacecraft will capture the sample canister in orbit and return it to the Earth.

There are no firm plans, though, for those later sample return missions after Mars 2020. In August 2017, NASA announced it was developing a “lean architecture” for sample return that focused on only the key capabilities needed for sample return. That approach would minimize the development of additional infrastructure, like a new communications and imaging orbiter that was previously under consideration.

On April 26, ESA and NASA signed a “statement of intent” to study potential cooperation in aspects of the Mars sample return architecture. The signing of the agreement took place during an international Mars sample return workshop in Berlin.

The announcement offered few details about any roles ESA might play, other than that a decision on a European role in future sample return missions would be made at ESA’s next ministerial meeting in late 2019. “The challenges of going to Mars and back demand that they are addressed by an international and commercial partnership – the best of the best,” David Parker, director of human and robotic exploration at ESA, said in the statement.

At an April 4 meeting of NASA’s Mars Exploration Program Analysis Group (MEPAG) in Crystal City, Virginia, scientists discussed sample return planning, including a study by a group called the International Mars Sample Return Objectives and Sample Team. That study, focused on the scientific objectives of Mars sample return, assumed that the effort would be carried out by more than just NASA.

“It’s going to be an international endeavor. We want everybody involved,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program, at the MEPAG meeting.