Why NASA Will Lose Contact With Its Mars Rovers for Two Days

The distant rovers and orbiters on our Red Planet neighbor are going dark for several weeks as the Earth pauses contact with Mars.

This is because Mars is passing behind the sun in our skies, garbling the signals being sent between the Mars tech and NASA on Earth.

This pause in communications—known as a moratorium—will last between November 11 and November 25, when Mars is due to be within 2 degrees of the sun in the sky, according to NASA.

NASA will continue to receive brief health updates from the rovers throughout this period, with the exception of a two-day stretch where Mars will be entirely hidden behind the sun's disc and the rovers will be totally unreachable.

"Outside of the two days, we will not lose contact with our Mars fleet," Andrew Good of NASA's Jet Propulsion Laboratory told Newsweek. "It happens every two years because that's when Earth and Mars are in places in their orbit where the sun is directly in-between them."

When Mars and the Earth are on opposite sides of the sun to each other, it's known as the solar conjunction of Mars. This occurs every two years or so due to the differing orbital speeds of the two planets: Mars orbits the sun every 687 Earth days. During this period, Mars is at its furthest point from the Earth at around 250 million miles, a much greater distance than at its closest point, where it is only 33.9 million miles away.

When Mars is so close to the sun in Earth's sky, radio signals being passed between the two planets may also travel through the sun's corona, a layer of hot, ionized gas that makes up the sun's outer atmosphere. This may corrupt and scramble the signals being sent to and from Mars and its rovers, possibly leading to data loss and weird behavior from the rovers that may endanger them.

The last time this moratorium occurred was between October 2 and 16, 2021, and before that, between August 28 and September 7, 2019.

"Our engineers have been preparing our spacecraft for conjunction for months. They'll still be collecting science data at Mars, and some will attempt to send that data home. But we won't be commanding the spacecraft out of concern that they could act on a corrupted command," Roy Gladden, manager of the Mars Relay Network at NASA's Jet Propulsion Laboratory in Pasadena, California, said in a NASA statement in 2019.

The rovers and orbiters won't be sitting around doing nothing during this time, however, as they will continue to collect data about the Red Planet to send back to us later, operating on autopilot, according to instructions sent by NASA in advance.

"Our mission teams have spent months preparing to-do lists for all our Mars spacecraft," Gladden said in a NASA statement this November. "We'll still be able to hear from them and check their states of health over the next few weeks."

The Perseverance and Curiosity rovers will stay stationary, but will carry on monitoring changes in Mars's surface conditions, weather, and radiation, while the Ingenuity Mars Helicopter will also stay grounded, but will use its color camera to study the movement of sand. In orbit, the Mars Reconnaissance Orbiter and the Odyssey orbiter will continue imaging Mars' surface, while MAVEN will collect data regarding interactions between the planet's atmosphere and the sun.

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Update 11/17/23 6 a.m. ET: The headline has been changed.