7 bizarre facts about the solar system that will amaze every scientist

In 1977, NASA’s Voyager 1 and 2 probes began their pioneering journey across the Solar System to visit the giant outer planets. Now the Voyagers are hurtling through uncharted territory on their way beyond our solar system. Along the way, they measure the interstellar medium, the mysterious environment between the stars that is filled with debris from long-dead stars. Voyager 1 became the farthest spacecraft from Earth in 1998, and no other spacecraft launched so far has a chance to catch it.

This 1997 artwork shows the planets of the Solar System and the relative trajectories of the first four spacecraft on course to leave the Solar System. In 1998, Voyager 1 overtook Pioneer 10, and in 2012, it passed through the heliopause and entered interstellar space. Voyager 2 entered interstellar space in 2018 and recently surpassed Pioneer 10 in 2023; therefore, we strongly suspect that Pioneer 10 is also in interstellar space, but is no longer functional, so we cannot make the critical measurements necessary to make such a determination.

Currently, five spacecraft are either on their way out of the Solar System or have already left it. From 1973-1998, Pioneer 10 was the farthest spacecraft from the Sun, but in 1998 Voyager 1 intercepted and missed it. In 2023, Voyager 2 also passed through it, and finally New Horizons will pass first Pioneer 11 and later Pioneer 10. In 2098, a gravitational rendezvous will give the now-defunct Ulysses spacecraft a gravitational kick, meaning 6 spacecraft are currently on their way to exit the solar system.

Transits of Venus (top) and Mercury (bottom) across the edge of the Sun. Notice how Venus’ atmosphere bends sunlight around itself, while Mercury’s lack of atmosphere shows no such effects. An airless planet like Mercury will have a completely flat transit spectroscopy spectrum, while a planet like Venus will show absorption and/or emission features.

Although our best views of the planets Uranus and Neptune to date still come from Voyager 2’s encounters with these worlds in the late 1980s, the two planets are actually extremely similar in color and composition, with the famous “cyan” image. Neptune does not represent his true color. Instead, Uranus and Neptune are very similar in color, as shown here.

This 2018 Hubble image of Uranus shows how the planet changes as it progresses from equinox to solstice. Cloud cover occurs at the bright North Pole, while clouds and streaks decrease over the rest of the world. Uranus will next reach the solstice in 2028.

This cutaway view of the four terrestrial planets (plus Earth’s moon) shows the relative sizes of the cores, mantles, and crusts of these five worlds. There are compelling similarities between Earth and Mars, as both have metal-rich crusts, mantles, and cores. However, Mars’ much smaller size means that both contained less heat overall to begin with, and that it loses its heat faster (in percentage terms) than Earth.

The image above shows an orthographic projection of the planet Mercury in this global mosaic centered at 0°N, 0°E. The radiating Debussy Crater is seen toward the bottom of the globe, and the Rachmaninoff Peak Annular Basin is seen toward the eastern rim. Mercury is the innermost and smallest planet in the Solar System and has been mapped in detail by NASA’s MESSENGER mission.

Although Earth and Venus are the two largest rocky objects in the Solar System, Mars, Mercury, as well as more than 100 of the largest moons, asteroids, and objects in the Kuiper Belt, have all reached hydrostatic equilibrium. Ganymede and Titan are larger than Mercury, but Callisto, at 99% the size of Mercury, is only one-third the mass of Mercury.

Of the eight planets in our solar system, the four gas giant worlds are the least dense, with less than half the density of the least dense rocky planet (Mars) and with Saturn even less dense than water.

As far as the large gasless worlds of the Solar System are concerned, Mercury has by far the largest metallic core relative to its size. However, it is Earth that is the densest of all these worlds, with no other large body to match its density, due to the added factor of gravitational compression. Unlike Venus, Earth and Mars, Mercury has no separate layer of crust to speak of.

The earth beneath its thin atmosphere and oceans transitions from a primarily rocky material to a metallic core once you go about 45% of the way down. At core pressures exceeding 3.6 million atmospheres, the atoms in the core are compressed to a fraction of their original size, which explains Earth’s atypically high density. Recent evidence suggests an innermost core within the inner core where a different solid phase of metals exists than in the rest of the inner core. All massive objects, including neutron stars, exhibit this type of pressure gradient.

The surfaces of the six different worlds in our Solar System, from an asteroid to the Moon to Venus, Mars, Titan and Earth, show a wide variety of properties and histories. While only Earth is known to contain liquid water precipitation and large accumulations of liquid water on its surface, other worlds have other forms of precipitation and surface liquids, both in the present and in the distant past. Perhaps, once upon a time, other worlds or even other planets like Mars and Venus joined Earth in holding liquid water and possibly life on its planetary surface.

Although Earth contains the most liquid water on its surface of all 8 planets, the most water in any form is found on Jupiter’s moon Ganymede. Next in order is Saturn’s Titan, Jupiter’s Callisto and Jupiter’s Europa. Planet Earth is only the 5th most water-rich planet, placing it ahead of Pluto, Dione, Triton and Enceladus, which land 6th to 9th in the Solar System.

Composed mostly of hexagonal ice crystals, a thick ocean of salt water extends an estimated 160 km (~100 miles) below Ganymede’s surface, making it the most water-rich world in the entire Solar System. . It contains more water than all other known stony worlds combined.

In Newton’s theory of gravity, orbits form perfect ellipses when they occur around a single large mass. The presence of other masses, like other planets, causes these elliptical orbits to precess. However, in general relativity there is an additional precession effect caused by both the curvature of spacetime and the fact that the planets are in motion relative to the Sun, and this causes the orbit to shift over time in a way that is sometimes measurable. Mercury exhibits the largest such effect in our solar system, processing at an additional rate of 43″ (where 1″ is 1/3600 of a degree) per century as a result of this additional effect.

By size, it is clear that the gas giant worlds far surpass any of the terrestrial planets, and this also applies to mass. However, in terms of proximity, the stone worlds are much closer to each other than the gas giants are to any of them or to each other. Both mass and proximity play an important role in determining how much a planet’s orbit will advance.

Hypothetical position of the planet Vulcan thought to be responsible for the observed precession of Mercury in the 19th century. An exhaustive search has been made for a planet that could explain the anomalous motions of Mercury in the context of Newtonian gravity, but no such planet exists, which distorts the prediction of an inner planet in our solar system. general relativity, another theory of gravity, instead explains this otherwise anomalous precession.