Callisto is the warmest Jupiter's satellite. Calisto /Io satellite Tmean temperatures comparison 134 K and 110 K

Tsat.mean.io = 110 K

Let's calculate Io's effective temperature old blackbody equation:

Te.io = [ (1-a) So (1/R²) /4σ ]¹∕ ⁴

Τe.io = [ (1-0,63)1.362 W/m² *0.0369 /4*5,67*10⁻⁸ W/m²K⁴ ]¹∕ ⁴ =

= (81.990.238,1)¹∕ ⁴ = 95,16 K



There is a big difference of


110 K - 95,6 K = 14,4 °C

Tsat.mean.callisto = 134 K ± 11 

Let's calculate Callisto's effective temperature old blackbody equation:

Te.callisto = [ (1-a) So (1/R²) /4σ ]¹∕ ⁴

Τe.callisto = [ (1-0,22)1.362W/m² *0.0369 /4*5,67*10⁻⁸ W/m²K⁴ ]¹∕ ⁴ =

= (172.844.285,7)¹∕ ⁴ = 114,66 K

Tsat.mean.callisto = 134 K ± 11

There is a big difference of

134 K - 114,66 K = 19,34 °C

So Callisto is warmer, no matter what.

Callisto is at the outmost distance from the Jupiter, so it cannot be warmed from the planet's IR, also because of the distance it has the lowest tidal effect.

But here it is what happens:


Callisto has (1 - 0,22) = 0,78 and Io has (1 - 0,63) = 0,37


That means Callisto "absorbs" twice as much solar energy


Callisto rotates 10 times less than Io, but Callisto has cp =1,

which is bid when compared to Io having cp = 0,145  

  Thus the (β*N*cp)¹∕ ⁴ for Calisto is (150*0,0599 *1)¹∕ ⁴ = 1,7313

does not differ much from the (β*N*cp)¹∕ ⁴ for Io, which is (150*0,5559 *0,145)¹∕ ⁴ = 1,8647

Io coefficient is ( 0,37 * 1,8647 )¹∕ ⁴ = 0,6899¹∕ ⁴ = 0,91137

Callisto coefficient is ( 0,78 * 1,7313 )¹∕ ⁴ = 1,3504¹∕ ⁴ =  1,07799

Callisto coeff /Io coeff = 1,07799 /0,91137 = 1,1828

Tsat.mean.callisto /Tsat.mean.io = 134 K /110 K = 1,2181

1,2181 /1,1828 = 1,029 or only 2,9 % difference !

Also the Io and Callisto have Φ = 1, when Europa and Ganymede have Φ = 0,47

So, all that together explains the reasons Callisto is the warmest Jupiter's satellite.