Phobos

Moon
Dimensions:26.8 × 22.4 × 18.4
Phobos Radius

Radius of Phobos

The radius of Phobos is one of its most fundamental physical characteristics. The Phobos radius measures approximately 11.1 km, making it 573.96× smaller than Earth. This measurement represents the average distance from the center of Phobos to its surface, providing crucial information about the celestial body's size and volume.

Understanding the Phobos radius is essential for calculating other important properties such as surface area, volume, and gravitational characteristics. The radius directly influences how we perceive and study this fascinating object in our Solar System.

Phobos Semi-Major Axis

Orbital Radius of Phobos

The Phobos semi-major axis is a critical orbital parameter that defines the average distance from the Sun. The Phobos semi-major axis measures 0.00 AU (approximately 9,378 km), which represents the average orbital radius of Phobos. This measurement is fundamental to understanding Phobos's position in the Solar System and its relationship with other celestial bodies.

The orbital radius of Phobos determines how much solar radiation the planet receives, which directly influences its temperature, climate, and overall environmental conditions. This distance places Phobos in a specific region of the Solar System, each with unique characteristics and scientific significance.

When we examine the Phobos semi-major axis 0.00 AU, we gain insights into the planet's orbital mechanics, including its orbital period, velocity, and the gravitational forces at play. This parameter is essential for space mission planning and understanding the dynamics of our Solar System.

Phobos Mass

Mass of Phobos in kg

The Phobos mass is a fundamental property that determines many of the planet's physical characteristics. The mass of Phobos in kg is approximately 1.06e+16 kg, which is 563396226.42× less than Earth's mass. This substantial mass creates a significant gravitational field that influences everything from atmospheric retention to orbital dynamics.

Understanding the Phobos mass allows scientists to calculate other critical properties such as surface gravity, escape velocity, and the planet's ability to retain an atmosphere. The mass also plays a crucial role in determining how Phobos interacts with other celestial bodies through gravitational forces.

The precise measurement of the mass of Phobos in kg is essential for space exploration missions, as it affects spacecraft trajectories, landing procedures, and the design of scientific instruments. This fundamental property helps us understandPhobos's formation history and its place in the evolution of our Solar System.

Phobos Orbital Period

How Long is a Year on Phobos?

The Phobos orbital period defines the length of one complete revolution around the Sun. The Phobos orbital period is 0.00 hours, which is 98956287.04× shorter than Earth's year. This orbital period determines the length of Phobos's year and directly influences seasonal patterns, climate cycles, and temperature variations.

The Phobos orbital period is directly related to its distance from the Sun, following Kepler's laws of planetary motion. Planets farther from the Sun have longer orbital periods, while those closer complete their orbits more quickly. This relationship helps explain why Phobos takes the time it does to complete one full orbit.

Understanding the Phobos orbital period is crucial for space mission planning, as it affects launch windows, travel times, and the timing of scientific observations. This fundamental orbital parameter also provides insights into the planet's formation history and its current position in the Solar System's dynamic structure.

How Far is Phobos from Earth?

Distance Between Phobos and Earth

How far is Phobos from Earth? This is a question that fascinates both astronomers and space enthusiasts. The distance between Phobos and Earth varies throughout their orbital cycles, but on average, Phobos is approximately 1.50e+8 km(1.000 AU) away from Earth. This distance changes as both planets orbit the Sun, with the closest approach (opposition) and farthest separation (conjunction) creating significant variations.

The question "How far is Phobos from Earth?" has practical implications for space exploration. This distance determines travel time for spacecraft, communication delays for mission control, and the amount of fuel required for interplanetary missions. Understanding this distance is essential for planning future missions to Phobos.

The distance between Phobos and Earth is not constant due to the elliptical nature of both planets' orbits. When Phobos and Earth are on the same side of the Sun (opposition), they are at their closest, making this the optimal time for observations and potential missions. Conversely, when they are on opposite sides of the Sun (conjunction), they are at their farthest separation, which can exceed the average distance significantly.

Physical Properties
Mean Radius
11.1km
Equatorial Radius
13km
Polar Radius
9.1km
Mass
1.06e+16 kg
Volume
5.78e+4 km³
Density
1.872g/cm³
Gravity
0.006m/s²
Escape Velocity
11.39m/s
Flattening
0
Average Temperature
0.0 K (-273.1 °C)
Axial Tilt
0°
Semimajor Axis
9,378km
Perihelion
9,234km
Aphelion
9,518km
Eccentricity
0.015
Inclination
1.075°
Sidereal Orbit
0.00 hours
Sidereal Rotation
0.00 hours
Mean Anomaly
0°
Argument of Periapsis
0°
Longitude of Ascending Node
0°

Overview of 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.

Physical Characteristics

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+4 km³, Phobos occupies significant space in the Solar System. The Phobos density of 1.872 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.

Orbital Properties

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.

Rotation and Tilt

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 indicates the planet's current position in its orbit relative to its perihelion. The argument of periapsis of shows how the orbit's orientation changes over time due to gravitational perturbations. The longitude of ascending node of defines the reference point where the orbit crosses the ecliptic plane.

Temperature and Atmosphere

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.

Escape Velocity & Flattening

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.

FAQs About Phobos

What is the gravity on Phobos?

The gravity on Phobos is 0.006 m/s² (1721.1× smaller than Earth's gravity). This gravitational force determines how objects behave on the surface, affects atmospheric retention, and influences the planet's ability to hold onto gases and particles. A person weighing 70 kg on Earth would weigh 0.0 kg on Phobos.

How big is Phobos compared to Earth?

Phobos has a radius of 11.1 km, making it 574.0× smaller than Earth's size. In terms of volume, Phobos is 0.0× the size of Earth. This size difference significantly impacts the planet's gravity, atmospheric retention, geological processes, and overall planetary characteristics.

How far is Phobos from the Sun?

Phobos orbits at an average distance of 9,378 km (0.000 AU) from the Sun, placing it 15952.0× smaller than Earth's distance from the Sun. This distance determines the amount of solar radiation the planet receives and significantly influences its temperature and climate.

How long is a year on Phobos?

A year on Phobos lasts 0.00 hours (98956287.0× smaller than Earth's orbital period). This orbital period defines the length of the planet's year and affects seasonal patterns, temperature variations, and the overall climate cycle.

What is the escape velocity of Phobos?

The escape velocity of Phobos is 11.39 m/s (982.1× smaller than Earth's escape velocity). This is the minimum speed required for an object to break free from the planet's gravitational pull and enter space. The low escape velocity makes it difficult for the planet to retain an atmosphere.

What is Phobos made of?

Phobos has a density of 1.872 g/cm³ (2.9× smaller than Earth's density). This density provides important clues about the planet's internal composition. The low density indicates a composition dominated by lighter elements, characteristic of gas giants or icy bodies.

Does Phobos have seasons?

Phobos has an axial tilt of . With minimal axial tilt, the planet experiences virtually no seasonal changes, maintaining relatively constant temperatures throughout its year.
Discovery Information
Discovered By
Asaph Hall
Discovery Date
12/08/1877
Raw Data