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The absolute ages given here are only approximate. From oldest to youngest, the time periods are: Pre-Noachian: the interval from the accretion and differentiation of the planet about 4.5 billion years ago to the formation of the Hellas impact basin, between 4.1 and 3.8 Gya. [13]
As on Earth, the sidereal year is not the quantity that is needed for calendar purposes. Similarly, the tropical year would likely be used because it gives the best match to the progression of the seasons. It is slightly shorter than the sidereal year due to the precession of Mars' rotational axis. The precession cycle is 93,000 Martian years ...
During the Noachian period (4.5 to 3.5 billion years ago), Mars's surface was marked by meteor impacts, valley formation, erosion, and the possible presence of water oceans. The Hesperian period (3.5 to 3.3–2.9 billion years ago) was dominated by widespread volcanic activity and flooding that carved immense outflow channels.
The sidereal year is 20 min 24.5 s longer than the mean tropical year at J2000.0 (365.242 190 402 ephemeris days). [ 1 ] At present, the rate of axial precession corresponds to a period of 25,772 years, [ 3 ] so sidereal year is longer than tropical year by 1,224.5 seconds (20 min 24.5 s, ~365.24219*86400/25772).
In astronomy, the rotation period or spin period [1] of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the sidereal rotation period (or sidereal day ), i.e., the time that the object takes to complete a full rotation around its axis relative to the background stars ( inertial space ).
The absolute age of the Noachian period is uncertain but probably corresponds to the lunar Pre-Nectarian to Early Imbrian periods [2] of 4100 to 3700 million years ago, during the interval known as the Late Heavy Bombardment. [3] Many of the large impact basins on the Moon and Mars formed at this time.
The bottom of the Jezero Crater – believed to have formed 3.9 billion years ago from a massive impact – is considered to be among the most promising areas on Mars to search for evidence of ...
Mars comes closer to Earth more than any other planet save Venus at its nearest—56 million km is the closest distance between Mars and Earth, whereas the closest Venus comes to Earth is 40 million km. Mars comes closest to Earth every other year, around the time of its opposition, when Earth is sweeping between the Sun and Mars. Extra-close ...