Phobos

Phobos is a fascinating moon in our Solar System that has captured the attention of astronomers and space enthusiasts alike. With a Phobos radius of 11.1 km, making it 574.0× smaller than Earth's size, this celestial body presents unique characteristics that distinguish it from other objects in our cosmic neighborhood. Positioned at an average distance of 9,378 km (0.000 AU) from the Sun, Phobos occupies a significant place in the Solar System's architecture. As a moon, Phobos demonstrates the incredible diversity of natural satellites that orbit larger celestial bodies throughout our Solar System.

The Phobos physical characteristics reveal a world of remarkable dimensions and properties. The Phobos radius measures 11.1 km, making it 574.0× smaller than Earth's size. The equatorial radius of 13 km and polar radius of 9.1 km create a slight flattening of 30.00%, indicating the planet's rotation affects its shape. The Phobos mass of 1.06e+16 kg represents 563396226.4× smaller than Earth's mass, giving this world substantial gravitational influence. With a volume of 5.78e+3 km³, Phobos occupies significant space in the Solar System. The Phobos density of 1.9 g/cm³ (2.9× smaller than Earth's density) provides clues about its internal composition, while the surface gravity of 0.006 m/s² (1721.1× smaller than Earth's gravity) determines how objects behave on its surface. The low density indicates a composition dominated by lighter elements, characteristic of gas giants or icy bodies.

The Phobos orbit reveals fascinating details about its journey around the Sun and its relationship to other Solar System objects. The Phobos orbit has a semimajor axis of 9,378 km (0.000 AU), placing it 15952.0× smaller than Earth's distance from the Sun. At its closest approach (perihelion), Phobos comes within 9,234 km of the Sun, while at its farthest point (aphelion), it reaches 9,518 km, creating a 3.0% variation in solar distance. The Phobos orbit is nearly circular with an eccentricity of 0.015 (1.1× smaller than Earth's orbital eccentricity), resulting in relatively stable solar heating throughout its year. The Phobos orbit takes 0.00 hours to complete (98956287.0× smaller than Earth's orbital period), defining the length of its year. The orbital inclination of 1.075° indicates how much the Phobos orbit is tilted relative to the Solar System's ecliptic plane. This low inclination means Phobos follows a path very close to the plane where most planets orbit, suggesting a stable formation history.

The Phobos rotation and axial orientation provide crucial insights into its daily and seasonal cycles, as well as its orbital dynamics. The Phobos rotation period of 0.00 hours (112588.7× smaller than Earth's rotation period) determines the length of its day. This extremely fast rotation creates intense centrifugal forces and may contribute to the planet's flattened shape. The Phobos axial tilt of 0° determines the intensity and nature of seasonal variations. With minimal axial tilt, Phobos experiences virtually no seasonal changes, maintaining relatively constant temperatures throughout its year. The orbital orientation parameters reveal additional details about Phobos's position in space. The mean anomaly of 0° indicates the planet's current position in its orbit relative to its perihelion. The argument of periapsis of 0° shows how the orbit's orientation changes over time due to gravitational perturbations. The longitude of ascending node of 0° defines the reference point where the orbit crosses the ecliptic plane.

The Phobos temperature and atmospheric conditions are fundamental to understanding its habitability and environmental characteristics. The Phobos average temperature of 0.0 K (-273.1 °C) (-459.7°F) provides the baseline for understanding its climate. These extremely cold temperatures make Phobos inhospitable to life as we know it, with any atmosphere likely frozen solid on the surface. Compared to Earth's average temperature of 15°C (59°F), Phobos presents a dramatically different thermal environment. Being closer to the Sun than Earth, Phobos receives more intense solar radiation, contributing to its temperature profile.

The Phobos escape velocity and shape characteristics reveal important details about its gravitational field and rotational dynamics. The Phobos escape velocity of 11.39 m/s (982.1× smaller than Earth's escape velocity) determines how easily objects can break free from its gravitational pull. This relatively low escape velocity means that gases and light molecules can easily escape into space, making it difficult for Phobos to retain a substantial atmosphere. The Phobos flattening of 30.0000% indicates how much the planet's rotation affects its shape. This significant flattening indicates rapid rotation that has substantially deformed the planet's shape, creating a pronounced equatorial bulge. The equatorial radius of 13 km compared to the polar radius of 9.1 km demonstrates this rotational deformation.