A surprisingly detailed picture of Mercury is emerging thanks to NASA’s MESSENGER mission that spent four years in orbit about the Sun’s innermost planet.
Mercury is a small, iron-rich planet that contains an unusually high concentration of volatiles (carbon, sulfur, sodium, potassium and chlorine). Volatiles can explode when molten magma is injected into an oxygen-poor environment or when dry, oxygen-free magma intrudes into a layer of volatile-rich material.
These elements can also vaporize at surface temperatures on Mercury and form hollows in the crust. These hollows may be a type of pyroclastic volcano or they may be a result of sublimation (melting) as vapors from volatiles sublime off the surface.
Some of these hollows are found in lava-filled craters, whereas others occur in older craters that were never flooded by ejecta or lava flows. This suggests that the volatiles were released from the underlying magma chambers, or that they were driven out by uplift of the surrounding lithosphere after they had been buried.
Other evidence of the presence of a large volume of vaporized magma is found in the shape of lobate scarps and wrinkle ridges on Mercury, which were produced by contractional faulting and deformation. These ridges are unique to Mercury and are interpreted as the surface expression of thrust faults that formed earlier in the planet’s history.
As Mercury cools, it contracts and reactivates its earlier thrust fault systems, forming lobate scarps on the intercrater plains. These scarps are similar to the ridges on the Moon, but are much larger. The ridges have steep scarp faces and gently dipping back slopes.
These ridges were formed as Mercury contracted during the Early Heavy Bombardment of about 3.9 billion years ago and are now largely buried by ejecta from impacts and lava flows. These lobate scarps can be hundreds of kilometers long and have large offsets of 1-3 km.
They are located throughout the intercrater plains and the Caloris Basin. They are largely composed of granitic rocks that formed from a mix of melt and magma, as well as from dike intrusions.
Mercury is also characterized by a rich diversity of impact craters, some of which are quite old, but many are young and feature halos of bright ejecta and prominent systems of secondary craters. Some of these craters are more complex than those on the Moon because their diameters are smaller. The difference is likely related to Mercury’s higher gravity, which keeps ejected materials from traveling as far from the crater as they would on the Moon.
Mercury’s atmosphere is one of the most tenuous in the Solar System, and it must be continually replenished. Fortunately, sources on the planet are constantly replenishing it, and Mercury’s magnetic field helps to deflect solar wind particles away from the surface.
The exosphere on Mercury is primarily made up of hydrogen, helium, oxygen, sodium, calcium and potassium gases. The atoms are released from the planet’s surface by solar wind, impacting meteoroids or outgassing of volcanic material on the planet’s surface.
These atoms are released with low velocities, which follow ballistic trajectories under the influence of gravity. Some of these atoms fall back onto the planet, while others drift off to form a comet-like tail that trails behind Mercury’s surface.
As Mercury is so close to the Sun, its gravity is weak and it cannot hold on to any significant atmosphere over long periods of time. This makes Mercury very hot and very dry.
However, it does have a thin exosphere, which is composed of atoms that were blasted off the planet’s surface by the solar wind or struck by meteoroids. These atoms are then pushed by sunlight to the outer reaches of Mercury’s atmosphere and then blown away.
The MESSENGER spacecraft is currently orbiting Mercury, helping to study this very tenuous exosphere and other aspects of the planet’s chemistry. It has been able to show that Mercury is not as iron rich as it was once thought to be, which has helped scientists understand why the planet’s surface is so different from that of Earth.
Moreover, the spacecraft has also been able to discover that Mercury’s atmosphere is dominated by sodium and calcium. These materials are mainly produced by processes related to solar radiation, but some of the atoms may have originated from the planet’s crust.
These findings provide more insight into the mechanisms by which Mercury’s exosphere is generated and maintained. They also reveal that the atmosphere of Mercury is very volatile and must be continuously replenished by sources on the planet.
Mercury, the planet closest to the sun in our solar system, experiences a wide range of temperatures. The surface can be hot enough to melt tin during the day and colder than ice at night, all due to its thin atmosphere and the nature of its orbit around the sun.
During the day, the surface of Mercury can reach a temperature of up to 800 degrees Fahrenheit (430 degrees Celsius), whereas at night it can drop to minus 290 degrees Fahrenheit (180 degrees Celsius). This is because the planet doesn’t have an atmosphere to hold onto the heat, but instead, the heat gets lost into space.
The surface of Mercury is dotted with bright streaks called crater rays, which are caused by the impact of rocks or other debris on the planet’s surface. When an asteroid or comet hits, the impact releases a tremendous amount of energy, which causes the surface to crack and crumble.
This crustal deformation caused the planet to have lobe-shaped scarps and canyons. These lobes are up to a mile high and can be hundreds of miles long.
But while this surface is abrasive and rough, it’s actually quite soft underneath, with an average thickness of only about 300 kilometers. That makes it the smallest planet in the solar system and is similar to Earth’s moon.
Its axial tilt is also much smaller than that of Jupiter’s moon Ganymede or Saturn’s moon Titan, meaning that it doesn’t experience seasonal variations in its temperature as they do on those planets.
Because of this, it’s very likely that there’s no life on Mercury, and that it never will. The extremes of the temperature on this planet would be too intense for any type of organism to develop.
Besides, the metallic mercury that is used in thermometers and barometers can damage the lungs and cause other health problems, such as nerve, brain, kidney and lung irritation. It’s also known to be toxic and can damage the skin, eye and ear tissues.
Mercury is the smallest planet in the solar system and also the closest to the sun. The cratered planet has no moons and zips around the sun faster than any other planet.
Because it lacks a large, stable atmosphere, the planet mercury can experience some wild temperature extremes. One side of the planet can be incredibly hot (800 degrees Fahrenheit, 430 degrees Celsius), while the other can be intolerably cold (-300 degrees Fahrenheit, -180 degrees Celsius).
The lack of an atmosphere means that the rocky surface can’t retain heat. This leads to extreme temperatures between day and night on mercury’s rocky planet.
On other planets, an atmosphere is like a blanket that redistributes the sun’s heat throughout the planet, but this isn’t the case on mercury. Instead, the sun’s heat is absorbed by the rocky surface and then released during the planet’s long nights before sunrise.
This leads to the most extreme changes in temperature in the entire solar system. During the day, the sun’s rays heat up the rocky planet to about 800 degrees F, while during the night it cools down to -300 degrees F.
As the rays from the sun hit the rocky planet’s surface, they break down hydrogen and oxygen molecules into hydroxyl groups. These OH molecules are the building blocks of water. The intense sunward heat energizes the hydroxyl groups to smash together, producing a water molecule.
These water molecules then freeze into ice on the icy surface of mercury, a phenomenon that has been confirmed by NASA’s MESSENGER spacecraft. These ice pockets are found only at the planet’s poles.
The researchers aren’t sure what caused this water ice, but it may have come from impacts or micrometeorites. Or it could be a result of mercury’s low tilt, which keeps its polar regions in shadow.
Nevertheless, these findings are very exciting. They indicate that as close as Mercury is to the sun, it still has a complex volcanic system and water ice in the deep craters of its north and south polar regions. The scientists said that these discoveries “could tell us a lot about the early history of Mercury.”