The Planets Closest to Earth’s Atmosphere

As you explore our Solar System, it is essential to determine which planets are the closest to Earth in terms of atmospheric proximity and why their atmospheres vary so drastically from each other.

Venus, considered Earth’s “sister planet,” can often be confused for being too hot; this is because of its thick carbon dioxide atmosphere which traps heat.

Venus

Venus, our cloud-shrouded sister planet, shines like a beacon in the post-sunset and pre-dawn sky, far outshining Mercury and Mars despite only being several astronomical units away. It’s easy to spot why; Venus’ thick atmosphere traps heat from the Sun and radiates it back out doubling its brightness.

Venus boasts some of the thickest clouds in our Solar System, covering it from top to bottom in layers that engulf its entire planet. A main cloud deck stretches 48 to 68 km (30 to 42 miles), with thinner hazes above and below it; unlike Earth’s clouds which reflect only 10% of solar radiation entering their atmosphere, Venusian clouds reflect 90%, meaning only a fraction of Venus ever shows itself from space despite being closer than any other planet to Sun.

Venus’ atmosphere varies significantly by region, but carbon dioxide (96%) is by far its dominant constituent, with minor amounts of nitrogen and other gases also present. Temperatures reach 300-310 Kelvin during daylight hours before dropping drastically at nightfall to drop back down again.

Scientists still are unsure as to the cause of the dark streaks seen throughout these regions; even under intense wind and rain they still absorb UV radiation from the Sun, giving rise to darkened regions with absorbent surfaces capable of absorbing its UV radiation.

Above the storms of Venus lies clouds composed of water droplets and other volatiles — including sulfuric acid — enveloping an expanse of volatile atmosphere. Therefore, freestanding scuba divers would quickly find themselves exhausted on Venus; atmospheric pressure there is nearly 90 times higher than on Earth, the equivalent to being one kilometer (0.6 mile) underwater! To explore this depth safely and responsibly, deep-sea missions use specially built submarines designed specifically for that task.

Venus has long been an uncharted frontier of space exploration, making its inhospitable climate difficult for probes from spacecraft like Soviet Venera probes from the 1960s and 1970s to penetrate its depths. These probes encountered extreme conditions on Venus that limited their lifespans severely – only Venera 13 (landing in 1981 for about two hours and collecting data) managed to gather any meaningful results. Now Roscosmos is considering an orbiter and lander mission called Venera-D that would attempt to explore this intriguing yet hostile planet’s secrets.

Mercury

Mercury, known for being Roman messenger of the gods, is the closest planet to our Sun and features an ultrathin atmosphere. As its days extend further than Earth, Mercury receives 10x more solar radiation; additionally, without an atmosphere, Mercury experiences very cold temperatures at nighttime.

Mercury’s surface features both smooth terrain and steep cliffs that can reach over one mile high, most likely caused by asteroid impacts that ruptured its crust; some were created by flowing lava deposits; this volcanic activity produces colorful mineral compounds on Mercury that scientists believe reveal information about its interior.

A 2016 study demonstrated that some of the planet’s volcanoes are covered with dark material composed of mostly carbon. While this material could have come from comet impacts, its likely source is more likely its own formation. Furthermore, this same research enabled scientists to observe that Mercury’s surface contains far less iron than was initially suspected due to earlier theories; perhaps due to how its core was initially much larger than its silicate mantle and material from it has since been lost through impacts events.

MESSENGER detected in its final orbits a 1.2-million-mile (2-million-kilometer) tail of neutral particles trailing behind Mercury as it traversed space. Although these particles have the same mass as Mercury, they are lighter because they do not carry heat from the Sun or its rays. Furthermore, the team found that its composition included materials similar to core-mantle boundary materials in abundance in this tail.

Mercury does not experience seasonal variations like Earth does due to its small axial tilt; instead it experiences thermal seasons caused by proximity to the Sun; observers on some places on its surface may witness sunrise and set multiple times per day on Mercury.

Earth

Venus is often referred to as Earth’s twin planet due to their similar size and composition, as they share many features such as proximity and atmosphere density. Furthermore, it boasts one of the hottest atmospheres compared to Mercury with an abundant carbon Dioxide layer keeping heat locked within.

Similar to Venus and Mars, Earth boasts mountains, valleys, volcanoes and ice caps; but unlike them it also boasts a thick atmosphere which not only supports life but provides protection from harmful radiation emanating from the Sun as well as an oxygen source through photosynthesis by plants.

The Earth is unique amongst planets in our solar system for having liquid surface water, with oceans covering about 70% of its surface area – this sets it apart from its icy siblings. Furthermore, Earth boasts the only large ozone layer that absorbs and destroys harmful ultraviolet rays – two factors which contribute to its unique status in terms of environmental preservation.

Scientists have utilized models to calculate how often each inner planet comes close to Earth, and have determined that Mercury takes 175 years on average before reaching its closest point, with Venus following in 2049 and Mars coming close in 2149. But these calculations only give part of the story, because they only account for distance. Therefore, researchers led by astronomer David Stockman ran simulations over 10,000 years in order to understand how often each of the inner planets comes close to our planet on average.

Venus occupies 47% of our closest solar system planetary relationships, followed by Mars at 36% and Mercury with only 17%. Zoozve is a small asteroid discovered in 2016 that represents our closest proximity – also the first quasi-satellite of any major planet ever detected and measured – approximately 200 feet across and orbiting at an estimated distance of 2.2 million miles (3 million kilometers from Earth or approximately nine times further away than its moon.

Mars

Mars, our nearest planet to Earth’s atmosphere, can be easily observed using a backyard telescope. Centuries of intensive observation by stargazers and spacecraft missions since 1960 have revealed that this red planet resembles our own in many ways – including clouds, winds, 24-hour days with seasonal weather patterns, polar ice caps and canyons or volcanoes that resemble those on our own planet.

Mars has an atmosphere only about one quarter as thick as our own due to a long history of volcanic activity that has sapped much of its carbon dioxide gas, leaving only a thin blanket of gases around the planet and its distance from the Sun for insulation and warmth.

At some point in its history, liquid water may have flowed across Mars’ surface and left temporary or long-term reservoirs of water in some spots; but whether life as we know it could exist there remains unknown; solar energy levels on this distant planet are only half that received on Earth and there is no protective magnetic field to ward against natural disasters.

Scientists have unearthed signs of wet pasts on Mars through erosion-proof sedimentary rocks and methane emissions from its atmosphere; further, a recent study suggests the Martian soil contains carbon-based molecules common among early life forms here on Earth.

On Tuesday evening, Mars will shine more brilliantly than it has in 60,000 years, making it easier to spot with naked eye observation. That’s because Mars has neared its closest approach to Earth since 15 years – an event not expected again until 2287.

The Red Planet and Mercury will soon meet up on Earth at their annual opposition, when both planets align in their orbits and can be seen from both sides of the Sun. According to NASA, their egg-shaped orbits have tilted slightly since their birth – something seen with Venus as well.