Update for 4 p.m. ET: NASA's Perseverance rover has successfully touched down on Mars! Read the full story here.
NASA's Perseverance Mars rover is scheduled to touch down on the Red Planet today (Feb. 18) at 3:55 p.m. EST (2055 GMT) — or at least that's when NASA will find out if it landed.
But by the time Earthlings hear from Perseverance for the first time since the landing attempt, the rover will have already spent at least 11 minutes hanging out on the surface of Mars. That's because it currently takes radio signals about 11 minutes, 22 seconds to travel between Earth and Mars, NASA said in a statement.
So, Perseverance's actual ETA, the time that it is supposed to land in Jezero Crater, is 3:44 p.m. EST (2044 GMT). But we won't know the exact time of landing — or whether the rover arrived intact — until 11 minutes, 22 seconds after the fact.
You can watch the Mars landing live here and on Space.com's homepage, courtesy of NASA, beginning at 2:15 p.m. EST (1915 GMT). The landing is expected at 3:55 p.m. EST (2055 GMT).
Related: How to watch NASA's Perseverance rover land on Mars
Live updates: NASA's Perseverance Mars rover mission
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At the time of Perseverance's landing attempt, Mars will be about 127 million miles (205 million kilometers) from Earth, NASA said in a mission description. (The planet's distance from Earth changes as the two planets revolve around the sun in their respective orbits.)
The radio signals that NASA uses to communicate with Perseverance and other missions travel at the speed of light, which is about 670,616,629 mph (1,079,252,848 kph). This cosmic speed limit means mission controllers at NASA's Jet Propulsion Laboratory (JPL) cannot instantaneously communicate with or operate the rover — or any other distant spacecraft, for that matter.
During the rover's landing, NASA's Mars Reconnaissance Orbiter (MRO) will act as a relay for lander radio communications. The orbiter will listen for messages from Perseverance and send information back to NASA's Deep Space Network of antennas on Earth.
Visit Space.com today for complete coverage of the Perseverance Mars rover's landing on the Red Planet.
Email Hanneke Weitering at firstname.lastname@example.org or follow her @hannekescience. Follow us on Twitter @Spacedotcom and on Facebook.