venus

since it's the easiest star to observe in the sky (a star, for the people of antiquity), it's the first subject of humans interacting with planets outside their own world. of course, since it's observed from our world in a pretty random manner, some ancient civilizations also treated venus from time to time as a different star.

probably because they lost the trip to the moon to the americans, the soviets got seriously hung up on this planet. while america was investing in the moon, these guys invested in venus. but of course, once again the usa surpassed the ussr on the venus matter too. even though the soviets came to have quite a bit of knowledge about venus thanks to the robots they sent, it was again the americans who mapped venus in detail. since landing on it and roaming its surface is pretty difficult (the average temperature on its surface is 465c), most states said "ah, forget venus for now" and focused on mars. for instance, the soviets' venera 13 is the craft most resistant to the venus environment, and it was able to operate for 127 minutes.

by the way, here's something interesting. it's thought that the planet actually ended up in this state because of the greenhouse effect. meaning our world too will maybe end up like this one day...