What is the Planet Closest to Earth in Size?

People frequently ask, “Which planet is closest to Earth in size?” Unfortunately, the answer lies within how distance is measured.

Kepler-452b, located 1,194 light years from Earth, is approximately 60% larger than Earth and orbits within its host star’s habitable zone, giving researchers reason to believe there’s an excellent chance it could support life.

Venus

Venus is the brightest planet in our solar system, yet is only slightly smaller than Earth. Its thick clouds reflect most of the light it receives from the Sun and thus appear as a brilliant star from Earth during sunrise and sunset – which ancients named Aphrodite after their goddess of love and beauty! Venus also stands alone as being devoid of plate tectonic activity on its surface.

Scientists speculate that Venus was once a fiery ball of molten lava similar to Earth. Over time, however, this hot lava slowly cooled and subsided deep within the planet until eventually creating an iron core and rocky mantle with an atmosphere composed primarily of carbon dioxide and sulfuric acid, 90 times thicker than our own and capable of boiling water instantly if present on its surface.

Due to Venus’ extreme greenhouse effect, its temperature reaches 864F (462C). This makes it the hottest planet in our solar system and second driest behind Mercury; thus denying life an existence on Venus.

Venus is often mistakenly believed to be closer to Earth than Mars due to a larger gap between their radii – however this only holds true at their closest approach. To get an accurate measure, we ran a computer simulation with PyEphem that charted all planets’ positions over 10,000 years and compared this result with PCM model’s average distances between planet pairs; on average Venus lies 1.14 AU away while Mercury sits closer at 1.04 AU.

Mars

Mars, one of the closest terrestrial planets, boasts the smallest radius but fifth-lowest mass among them – making it physically powerful among them all.

Mars is a reddish planet with red polar ice caps made up of frozen carbon dioxide and water molecules, unlike Earth, where an ozone layer provides protection from ultraviolet radiation. Mars’ thin atmosphere consists primarily of carbon dioxide (95%) and nitrogen (3%) with trace amounts of other gases like argon present.

Due to its elliptical orbit, Mars sways between nearer and farther from the Sun at different points throughout its annual orbital path, providing scientists with ample opportunity to study its surface with telescopes. Best observed during its perihelic opposition – when Mars comes closest to both Earth and Sun.

Last perihelic opposition took place in 2003 and isn’t scheduled to recur until 2035. While Mars will get closer in 2020 than 2035, this close encounter creates optimal launch windows for spacecraft missions to Mars.

Observing Mars requires an effective telescope, and now is an excellent opportunity to test one out. The Hubble Space Telescope will allow us to see surface features as small as three to six miles (5-10 kilometers), comparable to instruments on satellites that orbit Mars.

Astronomers have studied Mars since William Herschel first identified what he thought were oceans in its late 1700s surface, as pointed out by William Herschel in 1783. While William Herschel believed these dark regions on its surface to be oceans, lighter areas on Mars’ surface he believed to be continents. Mars features carbon dioxide-containing polar ice caps which cover its entire rocky surface; its thin atmosphere is composed primarily of carbon dioxide (95%) with some nitrogen (3%) plus other gases (1%) with trace amounts of oxygen present; in addition, both small moons Phobos and Deimos may have captured asteroids by Mars’ gravity over time.

Mercury

Mercury can be difficult to see in the night sky due to its proximity to the Sun; however, there are specific points throughout the year when its brightness peaks – this phenomenon is known as “greatest elongation,” and typically happens every two months or so. When at its most visible state it appears like a point of light in Scorpius while optical devices will resolve it as half-lit disc.

Mercury resembles that of the Moon closely, yet differs significantly due to its much denser atmosphere and metallic core, accounting for approximately 61% of volume versus only 4% on Earth. Mercury’s surface features smooth areas and craters with scarps rising from tectonic plates; such as Carnegie Rupes in Mercury’s northern hemisphere as reported by Live Science in 2019.

Caloris and Rachmaninoff, among many other impact basins, feature large impact basins filled with large impact crater basins that feature bright streaks called “crater rays”, caused by crushed rock particles reflecting sunlight back onto surfaces such as Rachmaninoff. Over time these crater rays become coated in space dust or solar wind particles.

Mercury, due to its small size and close orbit around the Sun, has only a tenuous atmosphere, leading to drastic temperature swings as it absorbs or loses heat from its star. Furthermore, such an environment makes Mercury vulnerable to solar winds that blast atomic particles into space – potentially damaging electronic equipment on Earth or other planets.

Neptune

Neptune, the third-largest planet in our solar system, lies approximately 30 astronomical units away from Earth (that’s a little less than half the distance between Sun and Earth). Like its gas giant neighbors, Neptune experiences seasonal changes and has its own set of rings and arcs surrounding its planet.

Neptune boasts some of the strongest winds in our solar system, often three times stronger than Jupiter and nine times stronger than any wind on Earth. These gusty breezes can whip clouds of frozen methane across its surface and even send blasts into space!

In 1989, Voyager 2 discovered the Great Dark Spot on Neptune. This large storm covers an area roughly equal to Earth and rotates anti-cyclonically; clockwise on one side and counterclockwise on the other.

Neptune boasts numerous spots – not only its Great Dark Spot but also bright white and dark spots on its surface – which may be caused by methane molecules in its atmosphere; however, scientists still have yet to figure out why Neptune appears so blue.

Neptune, one of our solar system’s ice giants, comprises about 80% or more of its mass and is made up of hot, dense fluid composed of “icy” materials such as water, methane and ammonia above its dense core. Being so cold, even traveling around its equator would take more than one year – as pressure keeps temperatures well below freezing on this distant world.

Earth

Though it might not seem so, Earth is actually the smallest planet in our Solar System and you could fit over a million Earths inside our Sun! That’s because most of it consists of space!

Earth is unique among planets in our Solar System in that liquid water has sustained life for most of its history. This is due to being located at just the right distance from the Sun, possessing necessary chemical ingredients for life, as well as having an atmosphere capable of supporting breathing and protecting us from its deadly radiation.

Discovering new worlds within our Solar System has taught us much about detecting habitable planets around other stars and their distance from them, including whether or not they can hold water. It has also demonstrated how important distance is in controlling surface temperatures of planets as well as whether or not they hold any.

Astronomers have recently discovered several Earth-size exoplanets orbiting other stars, with Gliese 12b being one of them and in its habitable zone of its host star. Furthermore, its closeness allows telescopes such as James Webb Space Telescope to scan its atmosphere for clues as to its oxygen content.

Kepler 186f is another Earth-size exoplanet orbiting a star that is similar to our own; this planet lies within its potentially habitable zone and features cooler and redder temperatures than our Sun; therefore it might host plant life that utilizes different colors than those seen on Green Planet.