Venus

Our sister planet, and the second planet from the Sun. Learn the secrets of Venus here!

Formation

After the Sun ignited hydrogen and began to supply energy to the Solar System, space around the Sun was immediately showered by a pressure wave of radiation, pushing the lighter gas and dust far out into the Solar System. Heavier rocky material was not affected, and over time collided to form larger planetesimals. These planetesimals fuel the planets’ formation as they fall under the gravitational pull of the increasing planetary mass, eventually forming Venus.

Composition

Like the other terrestrial planets, Venus has a silicate crust and a molten iron core. Venus is the third densest planet in the Solar System, with only Earth and Mercury being denser. Venus has a similar composition to the Earth, furthering the comparison of Venus as Earth’s twin.

Surface

The surface of Venus is riddled with craters, most of which are still in good condition thanks to the small amount of geological activity that Venus undergoes. The craters suggest that sometime between 300 to 600 million years ago, the surface of Venus stopped undergoing large amounts of geological activity. Venus has many larger volcanoes than Earth, though this is due to the age of the surface, which is about three to six times older compared to Earth, thus allowing more volcanoes to form. Most of the Venusian surface is dominated by volcanic plains. Two large, raised continents exist, one in the Northern hemisphere, Ishtar Terra, and one in the Southern hemisphere, Aphrodite Terra.

Atmosphere

Venus has an atmosphere that is 50 times denser than Earth, and 92 times the pressure at sea level, with the composition being mostly carbon dioxide. These extreme conditions cause the surface of Venus to reach temperatures of 850 degrees Fahrenheit! Since the atmosphere is so large, there is a layer that mimics the pressure and temperature of the Earth’s atmosphere at sea level. On Venus, this corresponds to 30 to 40 miles above the surface, making it the place with the most Earth like conditions in the Solar System. Absorption has been detected at those levels that may correspond to microscopic life absorbing the sunlight; however, this is still highly debated and not confirmed.

Magnetic Field

Venus has a small magnetic field compared to Earth, something which was unexpected considering the similar size and composition to the Earth. Unlike the Earth, Venus has a magnetic field that is created by the interaction between the ions in the upper atmosphere and the Solar wind. The internal mechanisms that drive Earth’s magnetic field were expected to create a magnetic field in Venus as well, despite the slow rotation of the planet compared to Earth. This may be due to Venus already having a solid core that no longer has any temperature gradient, but this is not known.

Satellites

The first successful mission to Venus was by Mariner 2, built by NASA to conduct a flyby of the planet. The goal of this mission was to measure the Venusian magnetic field and measure the temperature of the atmosphere, revealing the minimal magnetic field and the hot temperatures that exist on Venus.

Mariner 5 went to Venus to continue the mission started by Mariner 2, this time with more sensitive instruments to detect the magnetic field and atmospheric conditions.

Mariner 10 performed a flyby of Venus before reaching the final target of Mercury. On the passage, Mariner 10 took the first images of Venus and saw evidence for clouds at four different levels in the atmosphere of Venus. The atmosphere of Venus was also shown to complete a full rotation around the planet in four days.

The Soviet Venera 7 was the first probe to successfully land on Venus while transmitting data. Due to the extreme temperature and pressure, the probe only lasted 23 minutes before succumbing to the environmental conditions. Venera 8 soon followed and confirmed that clouds were present on Venus, ending at around 22 miles above the surface of Venus.

Venera 9 and 10 were the first satellites to enter orbit around Venus, measuring the ionosphere, magnetic field, and radar imaging the surface. The missions also contained landers that were sent to the surface, relaying the first images from the surface of another planet while collecting information on the composition of the surface.

The Pioneer missions were sent by NASA to Venus in two separate stages. The first mission sent a multiprobe satellite to send four probes into the atmosphere of Venus, measuring the atmosphere upon descent. The second mission sent an orbiter that lasted thirteen years and conducted seventeen science missions over the lifetime of the satellite. Pioneer was able to completely map the surface of Venus, revealing intricate details of the planet’s terrain.

Venera 15 and 16 entered orbit around Venus to map the surface and take detailed atmospheric measurements above the Northern polar region. The images were able to confirm that Venus had many more volcanoes compared to Earth and no tectonic plates or geological activity in the North region.

Magellan was launched to map Venus in the most detailed effort to date. Due to this detailed mapping, Venus was confirmed to have relatively few craters, leading to the conclusion that the surface of Venus is relatively young at only 300 to 600 million years old. Magellan also finally confirmed that Venus does not have any plate tectonics or current large-scale geological activity.

Venus Express was sent to Venus to measure the atmosphere over a significant time period. The orbiter was supposed to last less than two years but continued its mission until fuel was completely exhausted from the satellite. During the mission, Venus Express determined preliminary evidence for oceans once existing on Venus, along with a polar vortex over the Southern pole of Venus.

Akatsuki is an orbiter that was sent to Venus to image Venus in most wavelengths of the electromagnetic spectrum including ultraviolet, infrared, radio, and microwave. Initially Akatsuki was meant to enter orbit around Venus around 2010, but the maneuver failed causing the satellite to enter orbit around the planet in 2015 instead. Under Akatsuki measurements the Venusian equatorial jet stream was discovered, a fast stream of atmosphere near the equator. Akatsuki also detected a flash in the Venusian atmosphere, possibly observing lightning on Venus for the first time, though this is not confirmed. As of writing, Akatsuki is still performing science missions on Venus as of writing.