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Mercury Is The Smallest and Innermost: Mariner 10 Messenger Bepicolombo

Mercury is the smallest planet in the Solar System and orbits the Sun the fastest of all planets, completing its orbit every 87.97 days. It is named after the Roman messenger god Mercury. Mercury rotates in a unique 3:2 spin-orbit resonance that results in a day that is over 175 Earth days. It has the smallest axial tilt and largest orbital eccentricity of all planets. Mercury's surface is heavily cratered and it has extreme temperature variations from 100 K at night to 700 K during the day. Two spacecraft have visited Mercury to study it.

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31 views1 page

Mercury Is The Smallest and Innermost: Mariner 10 Messenger Bepicolombo

Mercury is the smallest planet in the Solar System and orbits the Sun the fastest of all planets, completing its orbit every 87.97 days. It is named after the Roman messenger god Mercury. Mercury rotates in a unique 3:2 spin-orbit resonance that results in a day that is over 175 Earth days. It has the smallest axial tilt and largest orbital eccentricity of all planets. Mercury's surface is heavily cratered and it has extreme temperature variations from 100 K at night to 700 K during the day. Two spacecraft have visited Mercury to study it.

Uploaded by

roberto
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Mercury is the smallest and innermost planet in the Solar System.

Its orbit around the Sun takes


87.97 days, the shortest of all the planets in the Solar System. It is named after the Roman
deity Mercury, the messenger of the gods.
Like Venus, Mercury orbits the Sun within Earth's orbit as an inferior planet, and its apparent
distance from the Sun as viewed from Earth never exceeds 28°. This proximity to the Sun means the
planet can only be seen near the western horizon after sunset or eastern horizon before sunrise,
usually in twilight. At this time, it may appear as a bright star-like object, but is often far more difficult
to observe than Venus. The planet telescopically displays the complete range of phases, similar to
Venus and the Moon, as it moves in its inner orbit relative to Earth, which recurs over its synodic
period of approximately 116 days.
Mercury rotates in a way that is unique in the Solar System. It is tidally locked with the Sun in a
3:2 spin–orbit resonance,[16] meaning that relative to the fixed stars, it rotates on its axis exactly three
times for every two revolutions it makes around the Sun.[a][17] As seen from the Sun, in a frame of
reference that rotates with the orbital motion, it appears to rotate only once every two Mercurian
years. An observer on Mercury would therefore see only one day every two Mercurian years.
Mercury's axis has the smallest tilt of any of the Solar System's planets (about 1⁄30 degree). Its orbital
eccentricity is the largest of all known planets in the Solar System;[b] at perihelion, Mercury's distance
from the Sun is only about two-thirds (or 66%) of its distance at aphelion. Mercury's surface appears
heavily cratered and is similar in appearance to the Moon's, indicating that it has been geologically
inactive for billions of years. Having almost no atmosphere to retain heat, it has surface
temperatures that vary diurnally more than on any other planet in the Solar System, ranging from
100 K (−173 °C; −280 °F) at night to 700 K (427 °C; 800 °F) during the day across the equatorial
regions.[18] The polar regions are constantly below 180 K (−93 °C; −136 °F). The planet has no
known natural satellites.
Two spacecraft have visited Mercury: Mariner 10 flew by in 1974 and 1975; and MESSENGER,
launched in 2004, orbited Mercury over 4,000 times in four years before exhausting its fuel and
crashing into the planet's surface on April 30, 2015.[19][20][21] The BepiColombo spacecraft is planned to
arrive at Mercury in 2025.

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