In science news around the world, scientists and physicians give mixed reviews to guidance abruptly issued by the U.S. Centers for Disease Control and Prevention that vaccinated people need not wear masks indoors or outdoors, with some exceptions. China becomes the second country, after the United States, to land a spacecraft on Mars and have it survive; scientists expect the Zhurong rover delivered by the Tianwen-1 lander will explore the Red Planet for about 90 days. Astronomers observe the highest energy light ever, gamma ray photons that they traced back to 12 likely sources in the Milky Way Galaxy, including a supernova remnant and, surprisingly, a nursery of baby stars. The Drug Enforcement Administration says it will soon end the University of Mississippi’s 53-year monopoly on supplying marijuana for U.S. research and give licenses to several other growing facilities. Billionaire Michael Bloomberg will donate $150 million to Johns Hopkins University and six other institutions to increase the number of Ph.D. students from groups underrepresented in science.