Here are my modifications, I think you'll find the plausible.
Mercury B30076A-F
Starport: B - Good, Refined fuel available, Shipyard (spacecraft) Repair, Naval 8+, Scout 8+, Research 10+, TAS 6+, Imperial Consulate 8+, Pirate 12+.
Size: 3 - 4,897 km
Atmosphere: 0 - None
Hydrographics: 0 - None
Population: 7 - 10,000,000 to 99,999,999.
Government: 6 - Captive government
Law Level: A - High
Tech Level: F - Research Base.
Venus B8D8868-F
Starport: B - Good, Refined fuel available, Shipyard (spacecraft) Repair, Naval 8+, Scout 8+, Research 10+, TAS 6+, Imperial Consulate 8+, Pirate 12+.
Size: 8 - 12,104 km
Atmosphere: D - Dense.
Hydrographics: 8 - 75% to 84%.
Population: 8 - 100,000,000 to 999,999,999
Government: 6 - Captive Government
Law Level: 8
Tech Level: F - research base.
http://wiki.travellerrpg.com/Terra_(system)
A few changes I will detail there.
Venus has a dense atmosphere of 96.5% CO2 and 3.5% N2, with an atmospheric pressure of 90 atm and an average surface temperature of 460o Celsius. Sulfuric acid rain falls in the upper atmosphere, but does not reach the surface.
Largely unexplored, manned expeditions beginning in AD 2830 revealed evidence of long extinct life, and that Venus had once been the site of an unfinished Ancients terraforming project that had been been interrupted (apparently) by the Final War. The current conditions on Venus are the result of the ensuing and uncontrolled runaway greenhouse. There is an orbital science station that still studies these Ancient ruins, of which most have been almost completely destroyed by the local environmental conditions.
In AD 2830, an expedition discovered the remains of an unfinished Ancients terraforming project, after studying it for half a century a means was discovered to reactivate the ancient apparatus, and the terraforming project was begun again this time under human management, by the time 1103 Imperial rolled around, Venus reached a stage where the upper atmosphere was breathable and inhabited, the habitable altitude begins at 16 kilometers above the surface with a breathable but dense atmosphere, at an altitude of 24 kilometers the atmosphere thins out to a standard atmosphere which is still breathable, temperature averages at 15 degrees centigrade at a latitude of 45 degrees, there are no appreciable seasons on Venus and the atmosphere super-rotates at this level once every 4 days. Most of the inhabitants of Venus live in floating structures at this level. The planet is still surrounded by a perpetual unbroken layer of clouds, most of the clouds are at the Dense level of the atmosphere where the temperature averages at 40 degrees centigrade. On the surface, the atmosphere is too dense to breath and the temperature averages at around 80 degrees centigrade but sometimes reaches as high as 100 degrees, though water doesn't boil at this pressure. The surface is covered with 76% water, the water is very hot, but hosts some specially adapted life which was adapted to survive at this temperature. The terraforming project is at this stage unfinished, but the planet nevertheless boasts a population of 400 million inhabitants. It is ruled by the daughter of the Duke ruling this system, Saphira Cleonestra Rohune. Saphira has to keep an iron grip on the inhabitants of this planet as many are Solomani sympathizers.
https://s-media-cache-ak0.pinimg.com/564x/c9/07/9e/c9079e7603bfad205a5770278ca39d89.jpg
