Mercury, our closest planet to the Sun, features heavily cratered surfaces with an abundant iron core.
Astronomers were once uncertain as to whether Mercury was tidally locked; one side always faces toward the Sun like our Moon does. There has been evidence of volcanoes on Mercury but none like those found here on Earth.
How did it form?
Mercury orbits closer to the Sun than any of the terrestrial planets and is also densest. A key reason is likely its metallic core; early development of Mercury likely consisted of more iron rich material compared to Venus or Earth, helping compress it into a hard, dense shell that quickly hardened over time.
Mercury’s proximity to the Sun means it is always bathed in bright light from its nearby stars, making its study difficult for scientists. That is why Mariner 10 had to pass by Mercury three times instead of just once to successfully do its mission.
That extra encounter provided a wealth of data on Mercury for scientists. They discovered a world full of craters, sulfur deposits, and days that last 88 days and years that last 176–not to mention an atmosphere so hot it bakes its northern regions to 500 degrees Celsius while chilling its southern half down to minus 200.
Scientists have several theories regarding Mercury’s formation. One is that it formed from an enormous impact, though such an event must take place under specific conditions: not too large, fast or sideways as this would cause massive mass loss and spin reversal.
As dust particles from the asteroid belt head towards the Sun, they may occasionally collide with Mercury and Venus. But their relatively weak gravitational pull cannot stop their passage; only something more massive like Mars can stop this migration through orbital resonance.
Chau and her colleagues discovered that large impacts rarely produced Mercury-like results in their simulations; instead they employed a hit-and-run approach in which an impactor whizzed past young Mercury without impacting it directly; more often than not this produced planets similar to Venus; the key being finding an impactor with just enough force to do just the trick.
What is it like?
Mercury lies so close to the Sun that it experiences extreme temperature swings during both day and night, without an atmosphere to trap Sun’s warmth; temperatures can fall as far as minus 275F! Romans named Mercury after its swift messenger god Mercury;
Mercury does not possess any moons, yet it circles the Sun more quickly than any other planet in our Solar System. Taking just 88 days, its highly elliptical orbit may take it as close to 29 million miles (47 million km) or as far away as 43 million miles (63.6 million km), making Mercury one of the more challenging planets to study from Earth.
Mercury is smaller than our Moon. From Mercury’s surface, however, our Sun would appear three times larger and seven times brighter than it does from Earth. Furthermore, Mercury lacks any water or atmosphere and features a heavily-cratered surface with an ancient molten core beneath that has since solidified over time.
Venus is the hottest planet in our Solar System due to its thick atmosphere trapping heat from the Sun. Without plate tectonics and instead boasting strange volcanic features like coronae and arachnoids that resemble pancakes, Venus boasts the hottest surface temperatures on our solar system.
Scientists speculate that Venusian arachnoids and coronae result from magma seeping out through cracks in its surface, although there’s no indication of subduction like there is on Earth. They do however believe that Venusian magma was once cooler and thus less dense.
Soviet space program achieved an astonishing technological accomplishment when they launched four Venera probes to Venus, returning images that show its surface as looking similar to Earth. Scientists know it once had thicker atmosphere; however, their reason behind its disappearance remains a mystery.
Where can I see it?
Tonight’s night sky will present stargazers with a rare solar system-wide show: Mercury, Jupiter, Mars and Uranus will align themselves, in what astronomers are referring to as a planetary alignment. Venus should be easy enough for stargazers to spot; she always remains one of the brightest objects visible even at dusk; but to view all five planets together effectively you’ll require a telescope.
Reasons behind this event lie within our solar system’s center of mass; all planets orbit in an almost circular fashion around this plane from time to time, often aligning onto it at once. As planets approach and move further away from each other in their orbits, their distance may appear greater or lesser depending on how their elliptical orbital paths line up with one another, making it unlikely for all planets to appear to be at equal distance from it simultaneously.
This planet parade can best be observed after sunset and before dawn when Venus is at its brightest in the west-southwest sky. On March 24, it will appear next to the moon and Mars (with its reddish hue), while Uranus may be harder to locate as it appears more like a greenish star than planet.
Timing and patience are the keys to spotting Mercury, along with a good vantage point. Your window for seeing it in the twilight near its peak elongation may only last several weeks, making the task of finding Mercury more of an art than science! Use binoculars or naked eyes and naked eye sightings combined with naked-eye observation as tools to tease it out of the glowing twilight; once seen, move your telescope toward its illuminated side which should face toward the sun – an effective way of testing your skill in finding celestial objects!
How long will it take me to see it?
Mercury, as one of the smallest planets in our solar system, orbits quickly around its sun. Unfortunately, due to no moons it can be difficult to identify with other planets; that is why Romans named it after their god of messengers; Greek astronomers sometimes called it both morning and evening stars.
But you can catch sight of our murky world if you look from the right spot at the right time. To do this successfully, a clear view of the horizon, binoculars or telescope, patience and time are needed; Mercury rises before and sets after the Sun so its brightness varies with proximity to both. Therefore, early morning or late evening twilight are optimal times to look for it.
Mercury will reach its brightest in late June, according to Hannikainen; however, it can still be difficult to see. Hannikainen recommends finding somewhere with an expansive eastward view and having binoculars handy; these tools can help bring Mercury out from behind its reflection from the Sun’s glare.
Arrive approximately 30 minutes prior to sunrise for optimal viewing conditions and remain until it starts darkening; any earlier and Venus will have moved too low into the horizon for you to have an effective look at her.
As an added treat, the waning crescent Moon may also be visible between Venus and Mars on certain days; and on June 24 it should be clearly above Venus making it easy to pick out in binoculars or telescopes. Exact timing will depend on your time zone – check online for exact times to head out! Remember that true north is 0, east 90 degrees, south 180 degrees and west 270 – use this information to locate Mercury or any other celestial objects on the horizon.