Many people think of Mars when talking about Earth's "sister planet." However, this article focuses on Venus, which is even more similar to Earth than Mars. 

Venus, known as the "twin brother" of Earth, is the second closest planet to the Sun in the solar system. It shares many similarities with Earth in terms of size, mass, volume, and distance from the Sun. Despite this, Venus is a lifeless planet due to its out-of-control greenhouse effect. 

Scientists believe that Venus may have had primitive oceans and land like Earth but lost them due to the extreme greenhouse effect. The runaway greenhouse effect on Venus led to the evaporation of all surface water and the destruction of any potential life. Venus's atmosphere is now composed mainly of carbon dioxide, making it the hottest and most inhospitable planet in the solar system. 

However, researchers suggest that the atmosphere 50 kilometers above the planet's surface could potentially be habitable for humans. NASA has proposed the concept of exploring Venus's high altitude as it provides an opportunity to gain experience and knowledge for future Mars exploration missions.