• The US space agency NASA has halted commanding its Mars missions for two weeks as Earth and the Red Planet are on opposite sides of the Sun.

• The period, called Mars solar conjunction, happens every two years. This year it falls between October 2 and October 16.

• While the missions on the Red Planet will continue collecting data, engineers back on Earth will stop sending commands to them until October 16.

What is solar conjunction?

• Solar conjunction is the period when Earth and Mars, in their eternal march around the Sun, are obscured from each other by the fiery orb of the Sun itself. The two planets are temporarily invisible to each other.

• Solar conjunction occurs every two years.

• The Sun expels hot, ionized gas from its corona, which extends far into space. During solar conjunction, this gas can interfere with radio signals when engineers try to communicate with spacecraft at Mars, corrupting commands and resulting in unexpected behavior from our deep space explorers.

• To be safe, engineers hold off on sending commands when Mars disappears far enough behind the Sun’s corona (the outermost part of the Sun’s atmosphere) that there’s an increased risk of radio interference.

• No one attempts to send new instructions to Mars during solar conjunction. 

• It’s impossible to predict what information might be lost due to interference from charged particles from the Sun, and that lost information could potentially endanger the spacecraft. Instead, prior to solar conjunction, engineers send two weeks’ worth of instructions and wait.

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