One of Mars 2020's heat shields cracked after a week-long series of tests, and NASA has no choice but to ask Lockheed Martin to build a replacement. The heat shield's purpose is to envelope and protect the Mars 2020 rover and landing system so they don't burn up when they enter the Martian atmosphere. Since the system will have to endure temperatures up to 3,800 degrees Fahrenheit, NASA and Lockheed Martin (its contractor for the mission) subjected the shield to forces up to 20 percent greater than what it'll encounter during entry.
Upon inspecting the shield, NASA found what it says is an unexpected fracture near its outer edge that spans its whole circumference. Lockheed Martin now has to build a new one for the mission, but it will also repair the damaged shield, so it can be used for more tests over the next year.
While unfortunate, the event is a perfect example of why the agency and private space companies have to put rockets, capsules and their individual components through rigorous testing first. Better to spend more on a replacement than lose billion-dollar spacecraft. In Mars 2020's case, the $2-billion mission includes a rover designed to look into the possibility of past life on Mars and to drill into the planet's surface to collect samples. The good news is that NASA doesn't believe the incident will affect its target launch in 2020 like what happened to the James Webb Telescope, so it doesn't have to think of a new name for the mission.