It's an exciting time to be alive for those passionate about astronomy. For the first time in years, it looks as if a manned mission to Mars is actually in the works, which would undoubtedly be the most astonishing human technological achievement in all of history. And the planet of Mars is fascinating- with the potential of water (either currently or in the past), signs of once-existent life, and of course any attributes it may have picked up as a result of science fiction throughout the 20th century.
However, something many are unaware of, is that Venus is actually a much more similar planet to Earth in many ways. Not only is it close in terms of size and density, but it also approximately ten million miles closer to home, making inter-planetary travel time for exploration much quicker than that of Mars.
Heat... Lots of it
Although Mercury is actually the closest planet to the Sun, Venus has the hottest climate of the entire Solar System. This is primarily caused by the runaway greenhouse effect as a result of its extremely dense atmosphere, which consists of around 96% carbon dioxide. It absorbs much of the Sun's heat and traps it beneath its thick clouds. In many ways, this is not unlike our own atmosphere here on our home planet.
It wasn't always this way. In fact, many millions of years ago, when the planets were cooler, it is believed that Venus had liquid oceans not unlike that which we have here on Earth. But as it heated up, along with the rest of planets over time, the thick atmosphere worsened and worsened the greenhouse effect to the point of literally boiling away all of the planet's oceans. And as sad as it seems, any of those oceans are now gone forever. The current temperature resides at around 900 degrees Fahrenheit, which doesn't exactly bode well for those who were looking for an inter-planetary fishing trip.
Cloaked in Mystery
Despite being the closest celestial object (other than the Moon of course) we know surprisingly little about our sister. In fact, due to the heavy sulphuric acid clouds spread across the planet, we were unable to view anything of the surface until the 1960s.
Even now, it remains a difficult place for exploration. The extremely high temperatures coupled with frequent electric storms cause the surface to be completely inhospitable for any life, and also interferes with a lot of exploration probes and equipment that scientists have sent to learn more. Not only that, but the pressure on the surface of the planet is about 12 times that of Earth, which results in most exploration equipment in being crushed before we can learn more.
The surface of the planet is littered with volcanoes; scientists are aware of thousands. Although most are believed to be extinct, however, it is thought that some have to still be active, as sulfur is thrown into the atmosphere in more than one location.
Although we have never been able to reach the surface and observe it firsthand, most agree that with the extremely high temperatures, active volcanoes, and electric storms (with no rain of course) that the planet may currently resemble what we know of as hell, with lots of dark and thick clouds and a desolate open landscape like you might find if our own oceans were to dry up.
Life, a Possibility?
Expert opinions differ on how long liquid water could have existed on the surface of Venus. Most scientists are in agreement that oceans existed for at least 600 million years, and some even are of the mind that they may have been around for up to two billion years. In this time, it would have been very possible for life to develop on the surface of the planet. However, these organisms would have long since died after the Sun continued to heat up and boiled away these oceans.
As for current alien life forms, most experts agree that it would be nearly impossible for the barren hell like surface of Venus to support life. However, there is evidence to suggest that extremophiles, small organisms that thrive in extremely hostile environments, could be alive today in the thick clouds surrounding the atmosphere. Much like we have thermophiles here on Earth, Venus may have small bacteria-like organisms that are able to survive in temperatures far above the boiling point of water. Of course, we currently do not have a good way to examine them, as these thick clouds have shown to be incredibly difficult to explore and learn more about. This is slowly changing though, and NASA has approved and is preparing for multiple Venus exploration missions within the 2020s.
What Can It Teach Us?
There is much to be learned from Earth's sister planet. Many experts in meteorology study the effects of out of control runaway greenhouse gasses on the planet, and apply much of the same studies to observe climate control and global warming here on Earth. Don't stress too much, as it is universally agreed upon that climate change to the extremity of Venus would be impossible here. Still, it provides compelling evidence as to why it is important to continually study the effects of carbon dioxide emissions to the atmosphere.
Plus... it's just really interesting. While the beautiful rings surrounding Saturn and the massive storms on Jupiter are interesting, these are gas planets and do not at all relate to anything we experience here on Earth. Whereas with Venus, a planet very similar to our own, the surface may have once been quite familiar to humans. Although it currently would be completely inhospitable, it is interesting to think about and draw similarities between man's interpretation of hell. And even though the surface water is likely to have been boiled away billions of years ago, in the scheme of the universe, that is just a few seconds ago. We may have missed out on a warm luxury resort by just a fraction of the age of our Solar System.