Mercury's average temperature is 430 C compared to Venus's 462 C.
Interestingly enough, even though being further away from the sun compared to Mercury, Venus is about 60 C hotter. To me, this seemed quite confusing at first: mercury is closer to the sun, shouldn't it be hotter?
After doing a quick google search about this phenomenon, it seems that the answer is in the atmospheric gases of each planet.
Mercury's thin atmosphere contains small traces of hydrogen, helium and oxygen. However, these gases are probably deposited by solar winds from the sun.
Venus on the other hand has a more dense atmosphere which contains a majority of Carbon Dioxide. CO2 makes up 96% of the atmosphere creating a strong greenhouse making it extremely hot.
So it seems that the dense atmosphere of Venus with CO2 makes it hotter than Mercury. Oddly enough... Earth's CO2 level is increasing at an unstable rate which is also causing a greenhouse effect increasing temperature. Not good....
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