Every 26 months Mars passes directly behind the Sun if to look from Earth. This arrangement, and the period during which it occurs, is called Mars solar conjunction. Radio transmissions between the two planets during conjunction are at risk of being corrupted by the sun's interference. US has three Mars orbiters and two Mars rovers and ESA has two orbiters. All Earth's control centers will refrain from sending commands to Martian spacecrafts during the period from July 22 to Aug 1.
Image: NASA
Out of caution, we won't talk to our Mars assets during that period because we expect significant degradation in the communication link, and we don't want to take a chance that one of our spacecraft would act on a corrupted command,
said Chad Edwards, manager of the Mars Relay Network Office at NASA's Jet Propulsion Laboratory, Pasadena, California.
This will be the eighth solar conjunction period for the Mars Odyssey orbiter, the seventh for the Opportunity rover, the sixth for the Mars Reconnaissance Orbiter, the third for the Curiosity rover and the second for the MAVEN orbiter.
Data will keep coming from Mars to Earth, although loss or corruption of some bits is anticipated and the data will be retransmitted later.
Source: https://www.nasa.gov/feature/jpl/for-moratorium-on-sending-commands-to-mars-blame-the-sun