Smallest planets in the solar system

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Mercury: The Smallest Planet in the Solar System

Mercury is the smallest planet in our solar system, with a diameter of about 4,880 km, making it only about two-fifths the size of Earth. In fact, some moons, such as Ganymede and Titan, are even larger than Mercury. This planet is also the closest to the Sun and is significantly smaller than all other planets in the solar system.

Mars: Another Small Planet

Mars is also considered a small planet, with a diameter of 6,792 km. It is larger than Mercury but still much smaller than Earth, ranking as the seventh smallest planet in the solar system. Its surface area is about 28% that of Earth, making it a relatively small terrestrial planet.

Sub-Earth and Sub-Mercury-Sized Planets Beyond the Solar System

Recent discoveries have shown that planets even smaller than Mercury exist outside our solar system. For example, the exoplanet Kepler-37b is significantly smaller than Mercury, with a size similar to that of Earth's Moon. This demonstrates that planetary systems elsewhere can contain planets much smaller than those found in our solar system48.

Smallest Planets and Exoplanet Discoveries

Space missions like Kepler have revealed that small, rocky planets—those with sizes between that of Mars and Venus—are common around other stars. These "sub-Earths" include planets with masses and sizes less than Earth's, and some are even smaller than Mercury. The Kepler mission has detected dozens of such sub-Earths, showing that the smallest planets are not unique to our solar system3810.

Conclusion

In summary, Mercury is the smallest planet in our solar system, followed by Mars, both of which are much smaller than Earth. However, discoveries of exoplanets have shown that even smaller planets exist elsewhere, including some that are smaller than Mercury. These findings highlight the diversity of planetary sizes both within and beyond our solar system1234810.

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Mercury the Sunshine Planet

Mercury is the smallest planet in our solar system, with a diameter of 2/5 of that of the Earth, and is the closest to the Sun, named after the Roman god of dealers and thieves.

2015·

0citations

·J. Benkhoff

Fourth Rock from the Sun

Mars is the seventh smallest planet in the Solar System, with a surface area of 144,798,500 km2 – 28% of the Earth's surface area – and a temperature of -290°C, making it the coldest planet in the Solar System.

2012·

0citations

·P. Grego

Occurrence and core-envelope structure of 1–4× Earth-size planets around Sun-like stars

Small, 1–4 Earth-size planets are extremely common around Sun-like stars, with 26% having them with orbital periods under 100 days, and 11% receiving 1–4 the incident stellar light that warms our Earth.

Highly Cited

2014·

83citations

·G. Marcy et al.

A sub-Mercury-sized exoplanet

Kepler-37b, a sub-Mercury-sized exoplanet, is likely rocky and without atmosphere or water, similar to Mercury.

Highly Cited

2013·

175citations

·T. Barclay et al.

Life and Death

This chapter explores the importance of asteroid, planet, and dwarf planets in our Solar System, examining their role in early Solar System conditions and their potential impact on our world.

2013·

0citations

·Michael Marett-Crosby

Kepler-78 and the Ultra-Short-Period planets

Ultra-short-period planets, like Kepler-78b, are common and often smaller than 2 R, often found in compact multi-planet systems, and may be the exposed rocky cores of "gas dwarfs".

Highly Cited

2018·

70citations

·J. Winn et al.

Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST

The James Webb Space Telescope can potentially detect the atmospheres of nine Earth-sized planets, allowing for the first time to probe the formation and evolution processes of terrestrial planetary atmospheres beyond our solar system.

Highly Cited

2017·

221citations

·C. Morley et al.

Below One Earth: The Detection, Formation, and Properties of Subterrestrial Worlds

Advances in astronomical instrumentation and space missions have made it possible to discover and study sub-Earths, with potential implications for planet formation and evolution.

2013·

8citations

·E. Sinukoff et al.

The HARPS survey for southern extra-solar planets. II. A 14 Earth-masses exoplanet around μ Arae

A 14 Earth-mass exoplanet has been discovered orbiting the star mu Ara, with a mass slightly smaller than Uranus, and may be considered an ice giant or super-earth planet depending on core-accretion and migration models.

Highly Cited

2004·

181citations

·N. Santos et al.

Advances in exoplanet science from Kepler

Kepler has revolutionized our understanding of extrasolar planets, revealing the typical characteristics of planets with sizes and orbits similar to Earth.

Highly Cited

2014·

90citations

·J. Lissauer et al.

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