Size comparison: Neptune vs Uranus

Size comparison between Neptune and Uranus. Both of these planets are gas giant planets with extremely cold surface temperatures. We see that these two bodies have the same size. Neptune is 1.5 times farther from the Sun than Uranus. The mass of Neptune is greater. Their rotation times are similar. Their surface gravities, their average densities, as well as their average orbital speeds are quite close. These two planets have a large number of natural satellites. Their composition is almost identical.

So how do you explain this color difference?

The cyan color of the planet Uranus is due to methane which has prominent absorption bands in the visible and near infrared.

Yet Neptune has the same methane content as Uranus, and its color is dark blue !? Scientists believe that Neptune has unknown compounds on the surface, which would explain this difference. So its color remains a mystery.

Next space missions for Neptune?

China intends to send a probe named IHP-1 (Interstellar Heliosphere Probes) which will leave in 2024 and reach Jupiter in 2029, then later Neptune (2032-2033?) And finally enter the limit of the heliosphere in 2049 to study there. heliopause.

NASA has a concept mission called Neptune Odyssey which could be launched in 2033 and which would aim to study the moons of Neptune, in particular the moon Triton.

The last time a probe came close to Neptune was Voyager 2 in August 1989, which goes a long way.

Upcoming space missions for Uranus?

The European MUSE mission should be launched in 2026 and reach Uranus in 2044. The probe will be effective until 2050.

NASA has several mission projects which are not yet very clear, and which could be launched in the late 2020s. Including the OCEANUS mission.

China will send its first exploration mission to Uranus in 2046.

We can say that we are sorely lacking information on these two planets. In addition, we do not have very good quality photos. It will take at least 15 hours for a probe to send information from Uranus, and 28 hours to send data from Neptune. It takes 8.5 years to reach Uranus under the most optimal conditions, and 12 years to reach Neptune.

Object	Neptune	Uranus
Type	Gaseous planet	Gaseous planet
Age	4.5 billion years	4.5 billion years
Diameter	49,244 km	50,724 km
Mean radius	24,622 km	25,362 km
Mass	1.02 × 1026 kg	8.68 × 1025 kg
Orbital period	164.8 years	84 years
Rotation duration	16 hours	17 hours
Surface temperature (average)	55 K -218 °C -360 °F	47 K -226 °C -375 °F
Surface gravity	11.15 m/s²	8.69 m/s²
Mean density	1.63 g/cm3	1.27 g/cm3
Orbital distance	4.5 billion km	2.95 billion km
Circumference	154,704 km	160,590 km
Surface area	7.6 × 109 km2	8.11 × 109 km2
Volume	62.5 × 1012 km3	6.83 × 1013 km3
Escape velocity	23.5 km/s	21.3 km/s
Average orbital speed	5.43 km/s	6.8 km/s
Aphelion	4.54 billion km	3 billion km
Perihelion	4.46 billion km	2.74 billion km
Semi major axis	4.50 billion km	2.87 billion km
Inclination	1.77°	0.77°
Satellites	14 natural satellites 1 quasi-satellite 0 artificial satellite	27 natural satellites 0 quasi-satellite 0 artificial satellite
Atmosphere composition	80% hydrogen, 19% helium, 1.5% methane, 0.019% hydrogen deuteride	83% hydrogen, 15% helium, 2.3% methane, 0.009% hydrogen deuteride
Distance from the Milky Way center	27,200 light years	27,200 light years

Note: if one of the objects is not visible, it just means that it is too tiny to be displayed compared to the other one.