How Far Is Mars From Earth? Distance and Signal Delay
Mars is about 55 to 400 million km from Earth, so radio signals take 3 to 22 minutes each way. Why the distance changes and what it means for rovers.
Mars and Earth both orbit the Sun at different speeds, so the distance between them is always changing.
- Closest: about 55 million km, when the two planets are on the same side of the Sun and Mars is near its closest point to the Sun.
- Farthest: about 400 million km, when they are on opposite sides of the Sun.
Close approaches happen roughly every 26 months. Mission planners use these windows to launch spacecraft, because the trip is shortest and needs the least fuel. A typical flight takes around seven months.
Signal delay
Radio waves travel at the speed of light, about 300,000 km per second. Even so, a message from Earth needs about 3 minutes to reach Mars at the closest point and about 22 minutes at the farthest. A question and answer can take up to 44 minutes.
That is why rovers cannot be driven live. Their drivers send a plan once per day and the rover carries it out on its own. Read more in how Mars rovers are driven.
Mars on your screen
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