On Monday, Jupiter will pass closer than ever before in 59 years – providing an excellent opportunity for telescopes and binoculars.
People often respond that Venus is the closest planet to our home planet; however, according to a new study this assumption is actually incorrect.
Venus
Answering “What is the closest planet to Earth?” usually produces Venus or Mars as possible answers, but is that truly accurate? Our Solar System revolves around an elliptical path around the Sun; therefore their relative positions change over time and therefore the best way to identify which one is closer in any given moment is looking at their average distance from it.
Most of the time, Venus is closer to Earth than Mercury; however, due to the elliptical orbits of both planets, this may not always be true. At times when its closest approach can reach up to 25 million miles from our planet while at other times it resides much further out at aphelion (160 million miles away from us).
Venus ranks second among all planets in terms of size and mass in our Solar System, yet remains an extremely hot planet with a toxic atmosphere composed primarily of carbon dioxide with occasional clouds of sulfuric acid sulfide vapors. Due to these atmospheric conditions, Venus remains the hottest planet with surface temperatures hot enough to melt lead; yet due to its extremely thick atmosphere (93 times denser than Earth at sea level), cooling off becomes almost impossible.
Venus’ atmosphere is so harsh that any possibility of life has long since vanished; nonetheless, many robotic spacecraft have flown past Venus or even made landing attempts on it over the years.
NASA’s Mariner 2 spacecraft became the first spacecraft to explore Venus when it flew by it in 1962. Subsequently, Soviet Russia became the world leader in Venus exploration by sending atmospheric probes and up to 10 landers there.
Due to Venus’ harsh environment, most robotic missions don’t last very long. One notable exception was Soviet Venera 13 which arrived on Venus in 1970 and sent back images of its surface; Japan’s Akatsuki spacecraft entered orbit in 2015 and still operates today.
Mars
The Red Planet has long been the subject of intense curiosity, and rightfully so. Humanity’s hope of eventually landing on another planet has become less sci-fi fantasy and more real possibility. If we could only visit one, which one would it be? Unfortunately, the answer might surprise you!
Venus is commonly thought of as one of Earth’s closest planets, but this may not always be accurate. Depending on where Venus falls in its orbit – at its furthest distance away it may reach 162-million miles; at its closest it may only be 33 million miles – meaning Venus can often come closer than Mercury!
Mars’ atmosphere consists of carbon dioxide and nitrogen with trace amounts of argon and water; combined with light dust on its surface, these gasses give Mars its characteristic tan hue, making it hard to see on some days. Craters dot its surface; including one called Valles Marineris that spans 10 times further and wider than Grand Canyon! There are north and south poles, plus frozen carbon dioxide caps.
As is true of Earth, Mars features seasonal cycles and an irregular axis of rotation which causes some parts of it to spin faster than others. Furthermore, Mars lacks any magnetic field so is vulnerable to radiation from the Sun; furthermore its rocky composition and thin atmosphere mean it remains extremely cold.
Mars boasts two moons: Phobos and Deimos, named for the horses who pulled Zeus’ chariot of war. Both moons are much smaller than our own Moon; Phobos is just 25 km (15.5 mi) across while Deimos measures 15 km (9.3 mi). Scientists suspect these could have been asteroids caught by Mars’ gravitational pull; our Mars-exploring rovers have earned themselves the moniker “Martian twins”, providing us with breathtaking images from its surface.
Mercury
Mercury, located in the innermost region of our Solar System, is a small planet teetering at its center. A metal-rich world with temperatures that can reach up to 840 degrees Fahrenheit and no atmosphere to trap heat or slow its cooling of its core, Mercury’s shrinkage rate has increased over time – possibly due to both gravitational effects from our Sun and its own rotational movement. As a result, Mercury continues its consistent decline. Recent research demonstrates this fast decline.
Scientists have conducted computer simulations of our Solar System and observed its movements over thousands of simulated years. Their research suggests that Mercury tends to orbit closer than Venus or Mars on average.
However, this does not hold true always due to their elliptical orbits; planets may sometimes come closer or further away than expected from each other depending on when Venus passes directly between the Sun and Earth (every 584 days) as its distance may exceed 93 million miles – this being its maximum possible proximity with our home planet!
Jupiter, Saturn, Uranus and Neptune all orbit about 10 to 30 AU away from Mercury depending on where their closest and farthest positions fall in terms of distance from it.
Mercury is one of the closest planets to Earth because its orbit is smaller than that of any of the others, meaning that it moves closer to the Sun more frequently and this was why Sumerians considered him both morning and evening stars.
Although scientists understand much about Mercury’s surface, they still lack an explanation for its giant iron core. One theory suggests a major impact stripped away much of Mercury’s silicate mantle during early Solar System formation, leaving its rocky core exposed. Another possibility suggests Mercury was more metallic than other planets during formation and some process caused its composition to include more iron than silicate during formation.
Jupiter
Jupiter, the fifth planet from our Sun, is an enormous gas giant with an immense magnetic field extending nearly 600 million miles out from its surface and tapering off into an extended tail of over 2 billion miles behind it. Its gravitational pull is two and a half times stronger than our own; standing on its surface would be similar to trying to stand in boiling water or walking through dense fog — if even visible at all!
Jupiter’s core may be so hot that its interior may consist of a swirling mixture of superhot gases rather than an unbroken solid ball. If its gravity were strong enough, any spacecraft or astronaut attempting to land there would likely be crushed under its weight by sheer atmospheric force and die instantly.
Jupiter orbits Earth at an elliptical angle, meaning that most of its time away from us lies beyond Earth’s grasp. When close enough however, its magnificent moons and rings can be observed using binoculars or telescopes.
Jupiter is home to vibrant light and dark bands created by an intricate network of wind currents in its atmosphere, where clouds composed of ice crystals, ammonia, or various chemicals can form and retreat as wind flows move across it. At its outer edge lies an ammonia cloud layer; further inward are dark clouds of various chemicals forming deep bands reminiscent of its depths. Finally, The Great Red Spot, a massive storm which rotates once every four to six days can also be seen wreaking havoc across its surface; see below
Voyager 1 and 2 spacecraft made their initial visit to Jupiter in 1979, taking stunning images of its Galilean moons with volcanic features and ocean depths revealed by Voyager images. Voyager also discovered Jupiter’s faint ring system while Galileo launched in 1995 to study its atmosphere until 2003 and discovered evidence for saltwater ocean on Europa.
The European Jupiter Icy Moons Explorer (JUICE) spacecraft will launch in 2023 and fly close by Ganymede, Callisto and Europa of Jupiter before exploring their intriguing properties up close in 2021. If any can support life they could become the focus of future missions that explore them more intimately.