You might wonder – which two planets have no moon? Mercury Venus Uranus and Neptune? In this article we will take a closer look at each planet to help you answer that question. You will learn what each one is best known for and which one is most similar to the other. Find out if you can guess their names based on their similarities! And don’t forget to share this article with your friends and family too!
Venus
It is a myth that you can see Venus and Jupiter in the same sky. The two planets actually have completely different positions in our sky so we can only see one when the Moon is in its place. The Sun rises at around 6:45 am in the Southern Hemisphere and sets at about 10:10 pm in the Northern Hemisphere. Both Venus and Jupiter will be visible during the dawn hour on February 27 2022.
It is difficult to say if Mercury and Venus had moons. Mercury is too close to the sun and its orbit is too sluggish. Venus is the only planet in our Solar System that does not have a moon. Mercury and Jupiter also have a sluggish orbit which makes it difficult to study their moons in detail. They do however have moons and astronomers are still studying them.
Although both planets are millions of miles away from Earth they appear close together from Earth. However if Venus were ever to approach Jupiter it would be pulled into its gravity and destroyed by its moons. If it was ever to get close to Jupiter this would give us a rare night sky show. The resulting right triangle would be spectacular and you’ll want to try and catch a glimpse. There’s still time to catch the conjunction between the planets.
Mercury is the closest planet to the Sun and is the smallest. As a result it should have a higher chance of hosting a moon. However Venus has a retrograde orbit and rotates in the opposite direction to most of the other planets in our solar system. In fact one Venus year is shorter than one day which makes it difficult to create a moon. This is because of Venus’ slow rotation.
Mercury
It’s a wonder that Venus and Mercury have no moons. The smallest planets in our solar system Mercury and Venus have very similar diameters to our Earth. At around twelve hundred and twenty-four kilometers Mercury and Venus have almost the same composition. But the Moon’s orbit is not stable; the Moon will fall back to the surface of Mercury within a few hundred million years due to tidal interaction. Moreover it’s impossible for the moon to stay close to the surface of Mercury for more than a few million years.
The reasons behind the lack of moons on Mercury and Venus are complex. Mercury is so close to the Sun that it can’t have had a moon during its formation. Venus is also a slow rotator so it would have been difficult for a moon to stay in orbit. And it’s possible that Venus had a moon at some point but it never got to stay in orbit. The MESSENGER spacecraft had to fire its thrusters two sets of times every 88 days to keep its orbit stable.
The size of a planet affects its chances of getting a moon. Larger planets that orbit near asteroid belts are more likely to have moons. However planets that are too close to the Sun rarely have moons. This is true for Mercury Venus and Mars. These planets were once so close to the Sun that they absorbed debris from the asteroid belt. However now the planets have moons the Earth has none.
The closest planets to the Sun Mercury and Venus have no moons. This is because they lack sufficient atmosphere to protect them from impacts and other natural disasters. This has resulted in their craters. A 60-mile-wide asteroid hit Mercury four billion years ago the equivalent of one trillion one-megaton bombs. Mercury is also home to a crater the size of Texas. Another large impact may have contributed to Mercury’s strange spin.
Another theory suggests that Mercury and Venus might have once had moons. However this theory isn’t confirmed. The two planets were created millions of years ago and it’s possible that a moon may have formed around Mercury and Venus before. The reason Venus and Mercury have no moon is unclear but scientists do know that they had a moon during the early stage of our solar system’s evolution. This process takes billions of years.
Uranus
Although Uranus and Pluto have no moons their interiors are mostly composed of hydrogen compounds. Compared to Earth Uranus’ moons are more rounded and have different compositions which can lead to questions about their origins. In addition to water Uranus also contains ammonia and methane. These compounds are similar to the elements found on Earth. Scientists believe that a rounded moon is most likely formed from rock and ice.
Until recently it was assumed that Pluto was much larger and more massive than it actually is. But images of Pluto’s moon PlutoCHARON showed that it was distorted by Earth’s atmosphere. This was made possible only by the Hubble Space Telescope which was the first to use adaptive optics to compensate for the effects of atmospheric turbulence. Now scientists can finally confirm the existence of Pluto’s moons.
The discovery of Neptune by European astronomers in 1846 had complicated the search for other planets. A closer look at Uranus’ orbit suggested that there was another planet outside Neptune’s orbit. In 1930 American astronomer Clyde Tombaugh discovered Pluto. This planet is three billion miles from Earth with a diameter of about two-thirds of the moon. While Uranus and Pluto have no moons they do have many neighbors.
The irregular orbits of Uranus and Pluto suggest that they are made up of rocky material. However they are loosely bound together implying that their origins are mysterious and unproven. Despite this it’s likely that rocky bodies formed in their respective planets. This is the explanation for why Pluto and Uranus have no moons. So what does this mean for us?
The Moons of Pluto and Uranus are not visible to the naked eye from Earth. Moreover Pluto is so far away that a Sun on it would appear 1000 times fainter than the Sun on Earth. That is why it cannot be seen with the naked eye and can only be seen with a telescope. The light from the Sun reaches Pluto in just over 5.5 hours. A telescope with an aperture of about 20 cm will be sufficient to view it. It is not known whether Pluto has any ring systems surrounding it.
Neptune
Though both Neptune and Pluto have no moon they share similarities in the solar system. Both have mysterious ring systems. Neptune’s outer ring named after American astronomer Carl Adams contains three arcs of bright material. This clumpy material may contain dust or other substances that could have chemical reactions with the planet’s atmosphere. The inner ring is much less well-known and is likely to be a diffuse band of material that contains a small amount of hydrogen and helium.
Pluto’s orbital characteristics are similar to those of Uranus. Its mass is about 12 times that of Earth. Since its discovery Neptune has not completed one orbit around the Sun. Its orbital period is about 165 years but it has not moved more than four degrees in the sky. The orbital period of both planets is too short for the formation of a moon preventing them from colliding.
The formation of the giant planets incorporated billions of icy planetesimals. During the formation of Neptune and Uranus many of these objects were scattered to the outermost regions of the solar system. During their formation these icy bodies were resonant with the orbits of Neptune resulting in a strange affinity between Pluto and Neptune. Because of this affinity the astronomers named these objects Plutinos which means ‘little Pluto.’
The outer solar nebula that contains Pluto and its four small moons was the same one that spawned these planets. The Pluto-Charon system consists of a cluster of icy bodies. Chiron is believed to be one of the icy planetesimals that contributed to this nebula. The outer solar nebula also contains a large number of comet nuclei that formed the Pluto-Charon system.
Before the reclassification of Pluto as a planet it was called a dwarf planet. This term was widely perceived as a demotion which led to a debate in the scientific community. In the 1950s the number of papers published on planetary science decreased dramatically. A large portion of them referred to mythical creatures and folklore. During this time almanacs made predictions based on the positions of only a few planets. The result was the perception that only the largest bodies in the solar system were planets.
