Five interesting facts about Venus, the Earth's evil sister
- Venus’ temperature is the hottest in the solar system.
- It is often described as Earth’s “sister.”
- Some people believe Venus could become a second home for humanity someday.
Venus is the second closest planet to the Sun and one of Earth’s immediate neighbors in the solar system. It is named after the Roman goddess of love and beauty, but its environment is actually hellish.
Venus’ temperature is the hottest in the solar system, not only because the planet is located about 67,000,000 miles (108,000,000 kilometers) from the Sun —which is, of course, closer than Earth, but further than Mercury, at around 41 million miles (65.5 million km) from the Sun—but also because its thick atmosphere is made up of greenhouse gasses (such as carbon dioxide) that trap heat near its surface.
In fact, Venus’ surface is hot enough to melt lead. It has a mean temperature of about 867ºF (464ºC). Lead would melt at around 621ºF (327ºC).
In spite of all this, Venus is often described as Earth’s “sister,” and some people believe it could become a second home for humanity someday, albeit, with quite a bit of effort.
So here are 5 interesting facts about planet Venus that you need to know.
1. Venus was once thought to be a star
Venus is one of the brightest objects in the sky. It can be spotted from Earth with the naked eye, although it follows a cycle in which it appears as a morning star for 263 days, then disappears for 50 days, and re-emerges in the evening sky, where it remains for another 263-days before disappearing below the horizon for 8 days, then reappearing as a morning star. This cycle led some ancient astronomers to believe that Venus was really two different stars, the Morning Star (visible after sunrise) and the Evening Star (visible after sunset).
Venus was later recognized as a planet. Because it is visible to the naked eye, there isn’t a single person credited for Venus’ discovery, but Italian astronomer Galileo Galilei was the first person who observed it with a telescope in 1610.
His observations confirmed Copernicus’ prediction that Venus had phases —just like the moon— depending on how close it was to the Sun. This fact proved that Venus orbited the Sun and not the Earth —something that favored Copernicus’ heliocentric model of the universe, at the time a controversial notion that discarded Earth as the center of the universe.
2. Venus was the first planet explored by a space probe
Although Venus can be easily spotted from Earth with the naked eye, observing the planet's surface isn't that simple.
This is because Venus is constantly surrounded by opaque sulfuric acid clouds that block astronomers' instruments.
Spectroscopic, radar, and ultraviolet technologies revealed a few details about Venus between the 1920s and the 1970s. However, most of the reliable data that we have about Venus comes from space probes.
The first one, Mariner 2, is also the world's first successful interplanetary mission. It collected data on Venus' atmosphere from over 21,000 miles (34,800 kilometers) above the planet's surface in December 1962.
In October 1967, the Soviet spacecraft Venera 4 calculated the temperature of Venus' surface and determined that its atmosphere was mostly composed of carbon dioxide (95%).
The first black and white images of Venus' surface came by way of Venera 9 and Venera 10 landers in 1975. Venera 13 and Venera 14 delivered the first color images in 1982. Venera 15 and Venera 16 mapped around 25% of Venus’ terrain in 1983.
This data was confirmed and amplified by NASA's Pioneer Venus Project from 1978 to 1992. The project included an orbiter and four probes which transmitted data during their descent to the surface. One probe survived the landing and was able to successfully transmit data from the surface for 67 minutes.
3. Colonization of Venus could be possible… perhaps through floating cities?
Venus has a hostile surface environment, not only because of its high temperatures but also because of its extreme atmospheric pressure. On Venus, the atmospheric pressure is around 92 times higher than that of Earth at sea level, which is equivalent to being half a mile (1 kilometer) underwater on Earth.
But in the upper-middle atmosphere, at the cloud-top level, things are different.
In 2003, NASA scientist Geoffrey A. Landis noted in his paper "Colonization of Venus" that at about 31 miles (50 kilometers) above the surface, the atmosphere of Venus is the most earthlike environment in the solar system other than the Earth itself.
He proposed that human exploration of Venus could take place using airships, speculating that one day, humanity could eventually build permanent settlements in the form of floating cities.
It might sound crazy, but in 2015, NASA actually developed the High Altitude Venus Operational Concept (HAVOC), a set of crewed mission concepts to explore the planet Venus from the least aggressive part of its atmosphere.
NASA described the mission as follows:
“A lighter-than-air vehicle can carry either a host of instruments and probes or a habitat and ascent vehicle for a crew of two astronauts to explore Venus for up to a month. The mission requires less time to complete than a crewed Mars mission, and the environment at 31 miles (50 km is relatively benign, with similar pressure, density, gravity, and radiation protection to the surface of Earth.”
4. Venus rotates on its axis in an unusual way
Most of the planets of the Solar System rotate anti-clockwise, but Venus, just like Uranus, spins clockwise on its own axis. In addition, while all other planets orbit the Sun in an anti-clockwise direction, Venus orbits the Sun anti-clockwise. Because Venus spins backward compared to Earth, the sun rises in the west and sets in the east on Venus. Because Venus' axis is not as tilted as Earth's (it's only 3 degrees), there are no marked seasons on Venus.
Venus' clockwise spin is called retrograde rotation, and one popular theory is that it was caused by the impact of a planet-size object in the past. This impact may also have knocked the planet upside down — Venus' poles are shifted by 180 degrees.
Venus also has a very slow rotation speed. One full rotation of Venus on its own axis lasts 243 Earth days. One rotation of Venus around the Sun is slightly shorter: about 225 Earth days. This means that a day is longer than a year. And, because of Venus' extremely slow rotation, it takes 117 Earth days to go from sunrise to sunset. The planet's atmosphere more considerably faster, however: it is able to complete a full rotation in four Earth days. Data from the Venus Climate Orbiter, launched in 2010 by the Japan Aerospace Exploration Agency, determined that the atmosphere moves so rapidly due to the presence of a thermal tide, a sort of atmospheric wave that is triggered by heating from the Sun near the planet's equator.
5. Venus has no moons
Just like Mercury, Venus doesn’t have a moon. This is probably because, just like Mercury, Venus is close enough to the Sun for any moons to be destroyed by tidal gravitational forces from the Sun.
Another hypothesis is that Venus did once have a moon, but the same big strike that reversed the planet’s spin also led to the moon developing an unstable orbit and crashing into the planet.