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Weirdest Wonders of the Solar System
Our Solar System
Eight Wonders in Our Astronomical Back Yard
Telescopes like Hubble can peer into deep space, discovering wonderful and terrible things like black holes, pulsars and distant galaxies.
For now, however, we are limited by the laws of physics to exploration of our own solar system. There is much to explore! We've barely scratched the surface -- quite literally -- of Mars and our own Moon. Beyond them is a dazzling array of sights that our grandchildren may one day visit.
Let's take a preview of some of the wonders of our solar system. I'll pick eight, one for each planet.
Mercury's Massive Core
Visiting Mercury is a challenge: it's so close to the sun that its inner face can top 800° Fahrenheit!
Its greatest surface feature is the Caloris Basin, the largest visible impact crater at a whopping 960 miles across. However, for the truly strange, we need to dig deeper. Mercury is so small that its interior should have cooled and solidified long ago. Yet radio waves reveal that Mercury's molten metal core is 85% of the planet. By comparison, Earth's core is about half its diameter. Cutting into Mercury is like slicing an egg and discovering it's all yolk!
The Twin Vortices of Venus
Venus has been described as Earth's "evil twin." The two planets are nearly the same size, however, Venus' sulfuric acid clouds and carbon dioxide atmosphere have produced a runaway greenhouse effect, heating the surface to a balmy 870° Fahrenheit.
The European Space Agency has discovered something even more extraordinary: enormous upside-down vortices spinning over both poles of the planet. Unlike Earth-based tornadoes and hurricanes, which suck upward, these vortices recycle the atmosphere downward. Furthermore, the north pole of Venus has not one but two of these vortices! Very bizarre.
Double, Upside-Down Hurricanes?
Earth's Tectonic Plates
Earth's Plate Tectonics
One of the groundbreaking discoveries of the 20th century was plate tectonics. Earth's crust is not solid, but divided into vast plates that move and grind against each other, emerging from undersea ridges and subducting under other plates.
This dynamic system produces earthquakes and volcanoes, but also provides most of our metal ores, the ingredients of modern technology. Without continental plates, which ride higher than oceanic crust, Earth might be a water world with isolated, scattered islands. Furthermore, recent geologic studies suggest that plate tectonics act as a thermostat, rescuing us from deep-freeze "Snowball Earth" periods when glaciers have reached the equator.
No other world that we have explored, save perhaps Jupiter's giant moon Ganymede, show signs of plate tectonics.
The Mariner Valley
Mars' Grand Canyon
Like Mercury, it's hard to pick just one magnificent feature on Mars. (And no, the so-called Face on Mars does not count).
Future Mars tourist guidebooks will focus on Olympus Mons, the largest volcano in the solar system. This Arizona-sized mountain is a hundred times larger than the largest volcano on Earth, and its base would cover Arizona!
However, Olympus Mons is easy to explain: low gravity coupled with a hot spot and lack of crustal movements allows lava to pile up in one spot. Less easy to explain is the Mariner Valley, a colossal trench that makes our Grand Canyon look like a sidewalk crack. Its dimensions are staggering: more than 2500 miles long (5 times the length of the Grand Canyon) and 4 miles deep.
Mars has lacked liquid water for billions of years. Besides, what kind of erosion could produce a canyon this long, this deep? Has the weight of all those volcanoes (including Olympus Mons) created a massive rupture in the planet's surface? One thing is certain: if not for Mars' thin atmosphere, the Mariner Valley would be a heck of a place to go hangliding.
Video: Soaring Through the Mariner Valley on Mars
Jupiter Compared to Earth
Jupiter's Great Red Spot
Sometimes old mysteries are the best. Astronomers Robert Hooke and J.D. Cassini first observed Jupiter's "Great Red Spot" in 1664-1665, and it's still there! This giant, long-lived hurricane is so huge that two or three Earths could span it side-to-side, and it towers 5 miles above the rest of Jupiter's cloud-tops.
Recent flybys from the Voyager, Galileo and Cassini spacecraft have given us a wealth of knowledge about Jupiter's atmosphere. We know that Jupiter's fast 10-hour rotation sends its gassy atmosphere whipping around it at hundreds of miles an hour. Without the friction of oceans or land, there is nothing to slow down Jupiter's storms, so they are surprisingly long-lasting.
Even so, the exact cause of the Great Red Spot's permanence and brick-red color are not yet known. It does change shape and color over time. In fact, it's shrinking, so even the Storm of the Millennium may not last forever!
Note: Click on this close-up of the Great Red Spot for a stunning view of this natural wonder.
The Hexagon on Saturn
If you thought the north pole on Venus was weird, check out this giant hexagon on the north pole of Saturn. Saturn, like Jupiter, is a gas giant, so the mysterious hexagon consists entirely of clouds. It looks like something out of a Stanley Kubrick film, but scientists Peter Read and Ana Aguiar of Oxford University's Department of Physics have been able to duplicate the hexagon using fluid dynamics in a laboratory (see that link for explanation and a video).
Right now, the hexagon is mostly in darkness during Saturn's winter, so we're stuck with infrared photos. I can't wait to see what it looks like in daylight. In the meantime, check out this fantastic rendering of the hexagon created by astronomy enthusiast Björn Jónsson using Cassini's photo plus a true-color photo of Saturn's north pole in partial shadow.
Hubble Shoots Uranus
Uranus, a Planet on Its Side
Uranus is unique in the solar system: it's lying on its side (axial tilt of 97.77°). This means that its day length varies dramatically. During summer or winter, its north or south pole points straight at the Sun, giving it permanent daylight while the other pole is plunged into darkness. On the spring and fall equinox, most of the planet enjoys a day of about 17 hours.
Even stranger, its magnetic field is tipped relative to its rotation. I have no idea how that is possible.
What caused Uranus' tilt? Astronomers guess that it's yet another victim of a protoplanetary collision (or perhaps two), but there's a problem. It's an ice giant: a gas giant like Jupiter and Saturn, but with more water, methane, ammonia and other elements that tend to freeze to ice at that distance from the Sun. If Uranus is all gas and free-floating ice particles, how could it "collide" with anything?
The accepted theory is that 32,500 mile-in-diameter Uranus consists of a 5,400 mile deep atmosphere surrounding a liquid ocean surrounding a rocky core slightly smaller than Earth. So it's just solid enough to get smacked around.
Neptune's Supersonic Winds
Cold, dark, and lonely Neptune is a scary place. Despite being named for the god of the sea, its winds are what really stand out. Recent timelapse photos from the Hubble Space Telescope (see video) show an average equatorial wind speed of around 700 mph — faster than the speed of sound! When Voyager 2 flew by Neptune in 1989, it measured the wind speeds around Neptune's "Great Dark Spot" streaming at up to 1,200 miles per hour.
Those are definitely the fastest winds in the solar system. I wonder if we'll ever be able to build a space probe capable of penetrating Neptune's atmosphere: it would certainly be a wild ride.