On March 7 and 8, morning twilight will bring with it a thin crescent moon floating near bright Venus and dim Mars as morning twilight arrives – binoculars may help you spot these two planets low in the east about one hour before sunrise.
Mercury is our closest planet — on average — as its orbit never takes it too far away from the Sun. However, astronomers know that averages don’t tell the whole story.
Mercury
Mercury, with its hot surface temperatures and unsolved mysteries, makes for an intriguing destination in space exploration. Yet from our view on Earth, its greyish-brown surface may not be all that captivating. Except if you look out for bright streaks of light known as “crater rays” that project out from its rocky surfaces. These streaks are caused by impact explosions from asteroids and comets striking Mercury with powerful impact explosions, leaving behind enormous amounts of energy that create large-scale excavation. Energy from impact also crushes smaller bits of rock, and these fine particles reflect sunlight more strongly than larger ones, giving crater rays their characteristic glow. Over time, however, their luminosity fades with exposure to space environment; but these glowing rays may still be seen during planetary opposition events when Earth rises east while Sun sets west.
While Venus may often receive more media coverage for being the closest planet to Earth, Mercury typically comes closer due to their orbits: closer they get to their parent body, the smaller their orbital radius becomes – meaning Mars can get close to both Sun and Mercury but cannot come closer than Mercury for us on average.
Mercury has the smallest orbit of all three inner planets, meaning its distance to Earth from one point in time is much less than those of Mars or Venus (and farther than Jupiter). This principle holds for each inner planet from Mercury through Mars to Venus.
NASA engineers from Los Alamos National Observatory recently published a paper in Physics Today showing that Mercury tends to be closer to Earth than Mars or Venus on average over a 10,000 year period. To achieve this result, computer simulation was run to track their positions over that period; results revealed that on average Mercury was closer than either Mars or Venus.
Venus
Venus, as the brightest, second closest and most stunningly beautiful planet in our solar system, has long been visible to humans since we turned our gaze skyward. Galileo made his first accurate observations using telescopes, with ancient people crediting Venus with beauty and inspiration – this belief later manifesting in sculptures like Venus de Milo.
Venus may seem inhospitable to life as we know it, with its extreme temperatures, strong winds and volcanic activity making conditions unsuitable for human settlement. Yet scientists believe its thick atmosphere of carbon dioxide may support microbiology – possibly by absorbing sunlight while protecting from UV radiation or providing nutrients necessary to create life molecules on its surface.
Venus is a rocky planet composed of an iron core, rocky mantle and blanket of carbon dioxide and nitrogen gases that blanket its atmosphere, as well as water vapor, sulfur dioxide and various other gases (argon, neon and helium), according to NASA. At its surface lies an unchecked greenhouse effect which makes Venus one of the hottest terrestrial planets.
Venus orbits within the inner Solar System, but due to its elliptical orbit it sometimes comes closer to Earth than Mercury. Venus rotates on its axis once every 243 days and its thick clouds reflect back 85% of sunlight that hits its surface.
Earth-like atmosphere of Venus contains 96% carbon dioxide and 3.5% molecular nitrogen with trace amounts of other gases such as sulfur dioxide, water vapor, argon and helium present. There is also some oxygen present – but only as the atomic kind – helping create an extraordinarily dense environment that has an average pressure of 95 bars, similar to Earth’s oceans.
Mars
Mars, our fourth neighbor from the Sun, can easily be seen with the naked eye or using telescopes. While inhospitable to life forms, its harsh landscape has fired our imagination and inspired robotic explorers such as NASA’s Perseverance Rover that are helping prepare for future human landings on its surface.
Mars may hold the distinction of closest planet neighbor, but due to how planets move in our Solar System, it doesn’t spend too much time as such. Astronomer David Stockman and colleagues conducted a simulation that tracked all planets for 10,000 years to find out for how long each one held that distinction – Mars being closest for approximately 17% while Mercury took up that title over twice as often – 47% overall.
Starting around the third week in March, observers at latitudes above 40deg North may begin noticing Mars rise into the twilight around 2 hours (Equator), 3 1/2 hours (Northern Tropics), or 5 hours (45deg South).
Mars reaches its highest point in late May, at about 26o west of Pleiades open cluster. After reaching this height in the sky, it travels rapidly west as it crosses Cetus constellation.
On June 12th Mars will pass 8o North of Alrescha (Psc or Alpha Piscium, mags +4.1 and +5.1). Also known as Alrischa, Alrisha or Al Rescha it consists of a blue-white pair separated by only 1″.8 East-West; telescopes of at least 75 mm (3 inch aperture) aperture are required to locate this fine target.
Mars began approaching Uranus at approximately 0.51o per day in mid-July, marking its fifth observable planetary conjunction of 2024-25 apparition. These two planets will meet annually at opposition in November; as Mars passes Uranus it will appear 0.2 magnitudes brighter while its daily apparent speed of motion will increase 17 times faster.
Jupiter
As is well-known, Venus is currently the closest planet to our homeworld; however, tomorrow (November 1-2) Jupiter will make an unprecedented close approach over 59 years – giving us an amazing opportunity to view one of our solar system’s biggest gas giants!
Jupiter should be easy to locate amongst the background stars of Aries constellation. It should rise shortly after sunset and remain visible for two or so hours before sinking below the horizon as twilight takes over.
Jupiter offers ample opportunity for stargazers, offering views of its 95 moons – many first identified by Galileo in 1610 when he first noticed Galilean satellites – an event often called Galilean satellites. As Galileo noted, the massive planet acts like its own mini solar system within our own, protecting Earth from thousands of potential asteroid impacts over the millennia due to its strong gravitational pull.
Jupiter is the hottest planet in our Solar System and features an oppressively hot environment made up of clouds and its fiery core. However, thanks to its powerful magnetosphere it also deflects comets and asteroids into more elliptical orbits, rather than colliding with Earth or its satellites. Thanks to its vast collection of moons Jupiter has long been an object of fascination for both astronomers and non-experts alike.
Jupiter will reach planetary opposition on November 1-2, just one day before passing between the Sun and Earth and reaching its maximum brightness for 2017. This rare chance to view this great gas giant may only last until 2024-25 when it repositions itself back in Aries.
The chart below displays Jupiter’s path through Aries and Taurus from March 2022-2025, depicting periods when it was unobservable due to proximity with or passage behind the Sun as black gaps on this chart. Jupiter will become visible again for Northern Hemisphere residents from late September 2023 until early May 2024 in evening skies, then again for Southern Hemisphere dwellers from March 2024-2025 morning skies; our online planetarium allows users to witness Jupiter apparitions more closely.