Mercury is the smallest planet in our solar system and features an extremely thin atmosphere. Additionally, its heavily cratered surface and extreme temperatures make it unlikely that any life could survive there.
No moon orbits it and it lies very close to the Sun. Best seen at dawn or dusk for optimal viewing; doing so during daylight could damage your eyesight.
It is the smallest planet in the solar system
Mercury, the smallest planet in our solar system, receives far less attention than Mars or Saturn’s moons. Although its orbit lies close to that of the Sun and surface temperatures are high, scientists still don’t fully understand its unusually large core.
Mercury resembles the Moon but is far denser, featuring an immense metallic core which accounts for 85 percent of its mass and an outer mantle and crust which make up its remaining 15 percent. Mercury lacks any tectonic plates and features only thin crustal layers.
Mercury’s surface is heavily cratered, featuring massive impact basins such as Caloris and Rachmaninoff Basins that stretch nearly 1000 miles in width, as well as ancient volcanoes dotted across its landscape. Although mercury lacks an atmosphere, there is still an exosphere composed of oxygen, sodium, hydrogen, helium and potassium; its magnetic field is generated by liquids at its core being stirred around, creating plasma around it that conducts electricity and forms its magnetic field.
Mercury orbits close to the Sun, with days lasting just 59 Earth days per year. Because its temperatures vary widely between hot and cold extremes, life unlikely to exist on its surface.
Due to being so close to the Sun, Mercury heats quickly and cools quickly as well. This causes its equator to be much hotter than its poles; however, due to weak gravity it cannot maintain an atmosphere and temperatures vary between 430 K during daytime to -173K during nightfall.
The Asteroid Belt lies between Mercury and the Sun, so it is constantly bombarded by meteoroids – this explains why its surface features many craters. Crater Rays form when an asteroid impacts, crushing some of its smaller fragments before hitting back at Earth with full force.
Mariner 10 was the first spacecraft to explore Mercury, mapping half its surface in 1974 and returning in 2004 with MESSENGER to survey its other half. Most recently, European mission BepiColombo launched in 2018 with plans to reach Mercury by 2025.
It has crater rays
Mercury, named for the Roman messenger god of the same name, is one of our Solar System’s smallest and densest planets. Without any satellites to keep its orbit around the Sun stable, Mercury accelerates faster than any other body around our Solar System – its unique composition making it a fascinating object to explore further.
Planet Earth is covered with greyish-brown surfaces dotted with impact craters of various sizes and long, bright streaks known as rays that form when an enormous amount of energy released during an asteroid or comet impact crushes and fractures the rock below it, creating more reflective surfaces than intact ones that cause the rays to shine brightly – however over time they may fade due to exposure to space environment.
Mercury is covered with craters of all sizes that litter its landscape, as well as intercrater plains similar to lunar maria that cover flat and smooth terrain similar to older crater terrain, sharing similar albedo readings as older cratered terrain. Many compression folds or rupes crisscrossing its surface are connected with thrust faulting and can also form boundaries to these plains.
Notable elements of Mercury’s landscape include lobate scarps and wrinkle ridges with steep scarp faces and gently dipping back slopes – these features may represent surface expressions of thrust faults that occurred in tandem with contraction and deformation of its crust.
Mercury does not possess a dense silicate mantle like that found on the Moon; instead it features a combination of silicates, molten iron and volatiles which combine into magma which rises through cracks in its crust to erupt as lava eruptions.
Contrary to Moon, Mercury contains few large multiring basins, with only the Caloris Basin known to exist. This may be the result of contraction and deformation on Mercury’s surface causing its lithosphere to rise higher over old basins obscuring them from view.
It has a dark side
Mercury is the smallest planet in our solar system and closest to the Sun, without any moons or satellites of its own. Mercury orbits fast around its star, making it appear three times larger and brighter when seen from Earth. It has areas covered with tectonic scarps as well as smooth plains where lava flows have filled craters – possibly contributing to Mercury’s rapid shrinkage over time.
Astronomers have discovered that Mercury’s surface contains volatile elements, such as sulfur and sodium. These findings support the theory that Mercury formed from an inner core composed of metals surrounded by an iron mantle before expanding outward to form planet-sized masses. Mercury’s high density, which cannot be accommodated within slow-and-gradual models of evolution, also reinforces this view of evolution.
Mariner 10’s images of Mercury revealed an unfamiliar world resembling that of our moon: covered with craters and vast, multi-ring basins; these ranged in size from 100 meters to over 1,300 kilometers and some had bright rays extending out from their edges; others had been degraded due to meteoroids striking and meteorite impacts; while the biggest craters are found within Caloris basin, likely caused by an early impact early in its history.
Mercury’s surface temperatures can reach extreme highs during the daytime hours, yet due to no atmosphere to retain heat at nighttime it quickly cools off significantly, making its likely development unlikely.
Mercury lacks an atmosphere, yet does possess a thin “exosphere”, made up of particles blasted off its surface by solar radiation, solar wind and micrometeoroid impacts – these particles quickly escape into space behind Mercury to form its tail of particles.
Mercury’s rotation period and orbit are extremely elliptical, leading it to appear retrograde when seen from Earth – this phenomenon known as retrograde motion or solar eclipse also happens when Mercury passes between Mercury and the Sun at different times during its orbital path.
It has no moon
Mercury orbits closer to our Sun than any other planet in our Solar System and moves around it faster than any of them. Without moon, any potential satellites would likely be swallowed up by solar wind before becoming visible to humans.
Mercury features a greyish-brown surface dotted with bright streaks known as “crater rays.” These occur when an asteroid strikes Mercury, creating an immense burst of energy which digs a massive hole while crushing huge quantities of rock into smaller particles that travel further before eventually falling back onto the surface where they form these bright rays. As fine particles of rock reflect more light than larger ones, making their brightness increase over time due to space dust and solar wind exposure.
NASA MESSENGER recently discovered evidence of water ice in some Mercury craters, suggesting that it had come from either comets or perhaps its interior when cooling and contracting over billions of years.
Mercury’s extreme temperature variations mean its surface can experience extreme hot and cold temperature swings throughout the day and night, making life unlikely to ever thrive on Mercury.
Mercury’s orbit leads it directly behind or in front of the Sun when seen from Earth, as seen from our perspective (inferior or superior conjunction, respectively). Mercury is sometimes hidden by the Moon during total solar eclipses; next one to happen will occur on November 12/13 2032.
Mercury can be difficult to spot with the naked eye, but using a telescope will greatly aid your observations. When looking through your telescope be careful not to point its lens directly at the Sun as this will blind yourself! A planetary guide app such as Star Walk 2 may make finding Mercury easier.