Mercury is the closest planet to the Sun, and the second-smallest planet in the Solar System. Mercury ranges from −0.4 to 5.5 in apparent magnitude, and its greatest angular separation from the Sun (greatest elongation) is only 28.3°, meaning it is only seen in twilight. The planet remains comparatively little-known: the only spacecraft to approach Mercury was Mariner 10 from 1974 to 1975, which mapped only 40–45% of the planet's surface.
Physically, Mercury is similar in appearance to the Moon as it is heavily cratered. It has no natural satellites and no atmosphere. The planet has a large iron core which generates a magnetic field about 1% as strong as that of the Earth. Surface temperatures on Mercury range from about 90-700 K, with the subsolar point being the hottest and the bottoms of craters near the poles being the coldest.
The Romans named the planet after the fleet-footed messenger god Mercury, probably for its fast apparent motion in the twilight sky. The astronomical symbol for Mercury (Unicode: ☿
is a stylized version of the god's head and winged hat atop his caduceus. Before the 5th century BC, Greek astronomers believed the planet to be two separate objects. The Chinese, Korean, Japanese, and Vietnamese cultures refer to the planet as the water star, 水星, based on the Five Elements.
The mean surface temperature of Mercury is 452 K, but it ranges from 90–700 K; by comparison, the temperature on Earth varies by only about 150 K. The sunlight on Mercury's surface is 6.5 times as intense as it is on Earth, with the solar constant having a value of 9.13 kW/m².
During and shortly following the formation of Mercury, it was heavily bombarded by comets and asteroids for a period of about 8000 million years. During this period of intense crater formation, the surface received impacts over its entire surface, facilitated by the lack of any atmosphere to slow impactors down. During this time, the planet was volcanically active; basins such as the Caloris Basin were filled by magma from within the planet, which produced smooth plains similar to the maria found on the Moon.
Apart from craters with diameters in the range of hundreds of meters to hundreds of kilometers, there are others of gigantic proportions such as Caloris, the largest structure on the surface of Mercury with a diameter of 1,300 km. The impact was so powerful that it caused lava eruptions from the crust of the planet and left a concentric ring over 2 km tall surrounding the impact crater. The consequences of Caloris are also impressive; it is widely accepted as the cause for the fractures and leaks on the opposite side of the planet.
The plains of Mercury have two distinct ages: the younger plains are less heavily cratered and probably formed when lava flows buried earlier terrain. One unusual feature of the planet's surface is the numerous compression folds which criss-cross the plains. It is thought that as the planet's interior cooled it contracted, and its surface began to deform. The folds can be seen on top of other features, such as craters and smoother plains, indicating that they are more recent. Mercury's surface is also flexed by significant tidal bulges raised by the Sun. The Sun's tides on Mercury are about 17% stronger than the Moon's on Earth.[1]
from wikipedia
Originally posted by BrUtUs:can it support life?