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The minimum distance between Earth and Mars has been declining over the years, and in 2003 the minimum distance was 55.76 million km, nearer than any such encounter in almost 60,000 years (57,617 BC). The record minimum distance between Earth and Mars in 2729 will stand at 55.65 million km.
It is known that in the past, Mars has had a much more circular orbit. At one point, 1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than that of Earth today. [188] Mars's cycle of eccentricity is 96,000 Earth years compared to Earth's cycle of 100,000 years. [189]
The astronomical unit (symbol: au[1][2][3][4] or AU) is a unit of length defined to be exactly equal to 149,597,870,700 m. [5] Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its modern redefinition in 2012. The astronomical unit is used primarily for ...
The gravity of Mars is a natural phenomenon, due to the law of gravity, or gravitation, by which all things with mass around the planet Mars are brought towards it. It is weaker than Earth's gravity due to the planet's smaller mass. The average gravitational acceleration on Mars is 3.72076 m/s 2 (about 38% of the gravity of Earth) and it varies.
In The Martian, by Andy Weir, the spaceship Hermes uses a constant thrust ion engine to transport astronauts between Earth and Mars. In Project Hail Mary, also by Weir, the protagonist's spaceship uses a constant 1.5 g acceleration spin drive to travel between the Solar System, Tau Ceti and 40 Eridani.
The maximum angular separation of the Earth and Moon varies considerably according to the relative distance between the Earth and Mars: it is about 25′ when Earth is closest to Mars (near inferior conjunction) but only about 3.5′ when the Earth is farthest from Mars (near superior conjunction). For comparison, the apparent diameter of the ...
The lowest energy transfer to Mars is a Hohmann transfer orbit, which would involve a roughly 9-month travel time from Earth to Mars, about 500 days (16 mo) [citation needed] at Mars to wait for the transfer window to Earth, and a travel time of about 9 months to return to Earth. [9] [10] This would be a 34-month trip.
A geostationary orbit, also referred to as a geosynchronous equatorial orbit[a] (GEO), is a circular geosynchronous orbit 35,786 km (22,236 mi) in altitude above Earth's equator, 42,164 km (26,199 mi) in radius from Earth's center, and following the direction of Earth's rotation. An object in such an orbit has an orbital period equal to Earth's ...