Venus vs Io (How Are They Different?)

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The main differences between Venus and Io is that Venus is the hottest planet in our solar system whilst Io is the most volcanically activate entity in our solar system, Venus is the 6th largest planet with a diameter of 12,104km whilst Io is the 4th largest moon with a diameter of 3,643 km and Venus is the brightest entity (other than the Sun) in our solar system whilst Io isn’t even the brightest moon.

There are various other differences between the two so continue reading if you want a more detailed breakdown of both celestial bodies along with their similarities and differences.

What Is The Planet Venus?

Venus is the 2nd closest planet to the Sun and is often regarded as Earth’s sister planet. It’s very close to our Earth in size where its diameter is 12,104km. This is just over 600km less wide than our home planet.

Unlike all the planets further outside the Sun’s orbit, Venus and even mercury have no moons orbiting it. The most probable reason for this is due to its closer proximity to it, which means that smaller objects orbit the Sun as opposed to Venus.

Venus is also the hottest planet in our solar system where its surface temperature is 475 degrees Celsius. This is due to a number of factors, like the thicker atmosphere, close proximity to Sun, the reasons for which have been explained in more detail here.

It’s core is hot too, similar to that of the ice giants and Earth, where it stands at 5,200 degrees Celsius.

As a result of this thicker atmosphere, Venus is also able to reflect a lot more of the light the Sun projects at it, making it both the hottest and brightness planet in our solar system. This is why for the longest time, and even till this day Venus is often referred to as the morning or evening star.

The thicker atmosphere is mostly compromised of carbon dioxide, and thick clouds of sulfuric acid. This does result sulfuric acid rain on the planets surface, which of course is very corrosive.

Being so close to the Sun also mean its orbital cycle is much shorter. It takes Venus 225 days to complete a full cycle, on the contrary a single day is actually longer than this where it takes around 243 days for a full rotation around its axis.

This is partially down to its distance from the Sun and the thick atmosphere surrounding this terrestrial planet. The axial tilt on Venus is also different from the other planets in our solar system where it is practically straight at 3 degrees.

All in all this is certainly one of the most interesting planets in our solar system and in many peoples eyes, could very well have supported life in the past based on how close its shape and size is to that of Earth.

What Is The Moon Io?

The Moon Io – also known as Jupiter I – is the third largest of the Galilean moons, which has the closest orbit to Jupiter. It is the fourth-largest moon in our solar system by size – with a diameter of 3,643km – but has the highest density of all moons in the Milky Way.

In addition, Io has the strongest surface gravity of all moons and the least water by atomic ratio compared to any other astronomical object in our solar system.

Perhaps the most interesting feature of this lunar body is the 400 active volcanoes on its surface, which make it the most volcanically active object in the Milky Way; some of these volcanoes can exude plumes of sulfur to a height of several hundred miles.

The reason for this intense activity is the tidal heating caused by friction in the moon’s interior. Thanks to Io’s proximity to Jupiter, it finds itself caught between the gravity of its planet plus the two nearby moons – Ganymede and Europa. And this creates extreme tidal forces.

A side effect of these tidal forces is heat, which keeps most of Io’s crust in liquid form. Because of this, the surface of Io experiences a constant state of renewal; sites once home to large craters are slowly filled with molten lava and liquid rock.

While the complete makeup of Io’s surface is not yet defined, theories suggest that its main component could be sulfur and sulfur compounds because of the varied coloring. Silicate rock could also be a likely component as it would account for the high temperatures.

Io orbits Jupiter from a distance of around 422,000km, with an orbit that takes 42.5 hours to complete. Sitting 778,000,000km from the Sun, the surface temperature of this planet sits around -130 degrees Celsius. But due to the intense volcanic activity, the lava flows can reach temperatures of 1649 degrees Celsius, which is far hotter than anything on Earth.

Similarities Between Venus And Io

Io and Venus do have their odd few similarities, which in this case includes the below:

  • Both have a hotter central core.
  • Both have an atmosphere and a rocky surface.
  • Both are a spherical shape.
  • Both are part of the same solar system.
  • Both have no rings surrounding them.
  • Neither have plate tectonics.
  • Neither have other moons orbiting them.

Differences Between Venus And Io

As for the differences between the two, they include the following:

  • Venus is the bigger of the two with a diameter of 12,104km compared to Io’s diameter that is 3,643km.
  • Io orbits Jupiter in an elliptical pattern whilst Venus orbits the Sun in a nearly circular pattern.
  • Io is tidally locked to Jupiter whilst Venus isn’t tidally locked to any other object.
  • Venus has an atmosphere 90 times the thickness of Earth’s consisting of 95.32% carbon dioxide, 2.7% nitrogen, 1.6% argon and 0.13% oxygen whilst Io has a very thin sulfur dioxide based exosphere.
  • Io is the most volcanically active entity in our solar system with 400 active ones on its surface whilst Venus’ volcanic activity is inconclusive although there is the possibility of 3 – 4 active ones.
  • A day on Io takes 42 hours whilst Venus completes a day in 243 days.
  • Venus orbits the Sun in 225 days whilst Io orbits the Sun in 12 years and around Jupiter in 42 – 43 hours.
  • Io’s density is 3.53 g/cm³ whilst Venus’ density is 5.24 g/cm³.
  • In regards to axial tilt, Venus’ is 3 degrees whilst Io’s is practically 0 degrees.
  • Venus is the hottest celestial object in our solar system with an average temperature of 475 degrees Celsius whilst Io’s temperature is -130 degrees Celsius.
  • As for mass, Io’s is 8.93 × 10^22 kg whilst Venus has a mass of 4.867 × 10^24 kg.
  • Venus has a gravitational strength of 8.87 m/s² whilst Io’s is 1.796 m/s².
  • Venus is the brightest celestial body (besides the Sun) in our solar system whilst Io isn’t even the brightest moon.


Even if Venus and Io are similar to each other in regards to their general composition and the fact that both have no other objects orbiting them, the two are still distinct when it comes to their overall functionality.

Whether it be in regards to the mass, size, temperature, brightness, thickness of atmospheres and more, Venus is simply designed to operate very distinctly from natural satellites like Io.

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