![]() (Credit: NASA) The exploration of Mercury This enhanced colour map taken by the MESSENGER probe shows the different types of rocks on the surface of Mercury. Mercury's exosphere is constantly evolving: while the solar wind continuously blows it away, intense gusts from the Sun also constantly super-heat more of the planet's crust, thereby replenishing Mercury's gassy envelope. For the most part, this outer layer is made up of particles coming from solar winds and elements from Mercury's crust (such as hydrogen, helium, oxygen and sodium) that are vaporized by the intense heat of the Sun. Mercury's atmosphere is so thin and fragile that it is instead considered an exosphere: a very thin volume of matter that surrounds a planet, but is not dense enough to behave like an atmosphere. Scientists believe that frozen water may exist in these craters. Some of Mercury's craters have shaded sections that are never exposed to the Sun. Mercury's surface remains the most mysterious of all the rocky planets, though, as no lander has ever explored it. Its surface is littered with craters that have accumulated and remained unchanged over billions of years, since the planet has no significant geological activity or atmosphere. SurfaceĪt first glance Mercury looks a lot like Earth's Moon. The opposite effect happens at sunset, with the Sun setting and briefly rising before finally setting completely. Because of this, the morning Sun appears to rise briefly, set, and continue rising again from certain spots on the surface of the small planet. Mercury's orbit is also the least circular of all the planets and looks somewhat egg-shaped. Just like Earth, Mercury also rotates on its own axis, but much more slowly: one day-night cycle on Mercury takes the equivalent of 176 Earth days, or two full Mercurian years! Mercury’s rotation in relation to distant stars takes 59 Earth days. Named after the Roman messenger of the gods, who was known for being very swift, Mercury takes only 88 days to complete one orbit around the Sun – the shortest year of all planets. The planet has a surprisingly large iron core, which may have formed because the early Sun heated and vaporized rock on Mercury's surface. Mercury is the closest planet to the Sun, which likely influenced its composition and formation. Our Sun was born at its centre, and the planets were created about 4.5 billion years ago from particles sticking together along rings in the disc. Instead, the inner planets relied on liquids and gases gathered from impacts and volcanic outgassing to form the atmospheres we see today.Īll this to say, the early building blocks of each planet contributes to our colorful planetary panoply.Like all the other planets, Mercury was likely formed in the large cloud of gas, dust and ice of the ancient solar system, which collapsed into a spinning disc. Whatever they did manage to pull in is unlikely to have lasted. ![]() But these young planets were unable to pull as much gas to themselves as their larger siblings. Iron, sulfur, aluminum, nickel, and other metallic compounds circled the baby Sun round and round for millions of years, crashing into each other, eventually coalescing into the inner planets. Jupiter, Saturn, and even Neptune and Uranus were able to pull in some of nebula’s hydrogen and helium to swaddle their cores, causing them to grow to truly massive sizes.Ĭloser to the Sun, the heat was so intense that it vaporized anything without high melting points only rocks remained. Most of the gas - predominately hydrogen and helium - was swallowed by our young star no surprise considering the Sun contains somewhere between 99.8 and 99.9 percent of the solar system’s total mass.Īt the same time, debris mixed into the nebula collided over and over again, eventually accreting into planetesimals and then protoplanets. But why are these planets so different?Īs it turns out, stars and their planets form at the same time from a disk of gas and dust known as a solar nebula. Even the gas giants are different, Neptune and Uranus an opaque blue, while Jupiter and Saturn are mostly beige with brilliant red-brown belts. Mercury is slate gray while Venus is pearly white, Earth a vibrant blue, and Mars a dusky red. The planets of the solar system are varied in their appearance.
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