Explaining ‘the Goldilocks Zone’ for life on planets
It’s not too hot.
It’s not too cold.
It’s just right.
And it’s why that sweet spot in its distance from a star at which a planet can sustain life is called the Goldilocks Zone.
“Our sun has this combination of radius and temperature that’s kind of in the middle range,” says Dan Fleisch, professor emeritus of physics at Wittenberg University. And Earth’s distance from it — roughly 93 million miles — is smack in the zone.
At half that distance, “We would be exposed to four times the intensity of sunlight, which would have devastating effects on our environment,” Fleisch said.
In the opposite direction, Mars — which is half again farther from the sun than Earth — gets “less than half of the energy from sunlight we do,” he said.
Why less than half? Because as the distance from the sun increases, its rays spread out and cover a larger area. As it enters our atmosphere, sunlight delivers about 1,400 watts per square meter of energy. On Mars, that’s reduced to around 600 watts.
The key factor in the Goldilocks Zone — the one necessary to sustain life — is the relationship between temperature and water. For life as we know it to exist, water can’t be frozen all the time, and there are limitations that come with its vaporized form.
Now knowing the most important thing about our home planet here in the Goldilocks Zone, we’ll take a glimpse at some others in and out of our solar system. And who better to guide us than Fleisch, an Ohio Professor of the Year and a man for whom the International Astronomical Union has named a minor planet that’s orbiting right now in the asteroid belt between Mars and Jupiter.
THE TERRESTRIAL PLANETS MERCURY: DUST IN THE SOLAR WIND
Hugging the curve of its inside orbital lane, Mercury laps the sun in a fourth of the time it takes earth. Other “mercurial” traits: Its temperature spikes at 800 degrees Fahrenheit and plunges to 300 below every day due to its weak atmosphere.
British scientist Dave Rothery focused on another aspect of the planet three years ago in a BBC story aired after the international Bepicolombo mission’s first Mercury flyby.
Images showed the expected “cratered surface,” he said, (but) “there now is evidence of planetary erosion.”
Next year, when the spacecraft enters a stable orbit around Mercury, and “we see really high-resolution images,” he predicted, “you’ll see that the top 10-20 meters of the surface is dissipating to space” — like dust in the solar wind.
VENUS: WHAT NOT TO LOVE
From space, says Fleisch, “all you see is white, because of the (Venusian) clouds.”
Thousands of kilometers thick and laden with sulfuric acid, they mask a planet in which temperatures of 850 degrees Fahrenheit constantly vaporize planetary liquids and power ceaseless storms.
Fleisch is among an army of scientists who say that Venus’ once Earthlike
conditions were undermined by greenhouse gases, mostly carbon dioxide and methane, thought to have been spewn into Venus’ atmosphere by volcanoes.
Such gases warm the planet by trapping the heat from infrared rays in sunlight and emitted by warm surfaces that otherwise would pass through the atmosphere and out into space. Like quarter teaspoons of cinnamon or cloves added to pumpkin pie, he said, greenhouse gasses have “a wildly oversized effect.”
“If Earth were the size of a cueball,” he said, “the atmosphere would be as thin as a piece of paper wrapped around it. As we’re seeing, it doesn’t take much to disturb the delicate balance in the skinny envelope that’s keeping us alive.”
FRACTURED CRUST PIZZA ON MARS
“The gravity on Mars is only about 38% of ours,” Fleisch said, “so volcanos can grow much bigger there.”
And at 13.6 miles high — two and a half times as high as Mount Everest and with an area larger than Texas — Olympus Mons would be a must stop for tourists on Mars.
The other supersized attraction would be Valles Marineris, a 2,500-mile-long canyon in the Martian surface where the Grand Canyon could get lost.
Fleisch said that when our solar system was “a celestial shooting gallery” several billion years ago Mars “suffered an impact that almost broke the planet” and created the valley.
“Volcanic and some type of uplift process” gave rise to the ‘Tharsis Bulge’ near Mars’ equator and fractured the planet’s crust.
And really, what family visiting Universal’s Tharsis Bulge Resort could resist the Asteroid Impact Ride and a slice of Fractured Crust Pizza?
THE JOVIANS: On the outer limits
At the outer limits of our solar system are the Jovian planets Jupiter, Saturn, Uranus and Neptune. All, says Fleisch, are “farther from one another than the Earth is from the sun” — and are of a different order.
None has a solid surface; all are several times larger than Earth, and every one of them has multiple moons. Jupiter and Saturn have more than 80 each.
Here are thumbnail sketches of the Jovians
condensed from the website of The Planetary Society (where more information is available).
Twice as massive as any every other object in our solar system combined
(save the sun), Jupiter is considered a planetary system of its own, in part because of volcanoes and sub-surface oceans on two of its four largest moons. Scientists think its persisting red spot is an Earthsized hurricane that’s been raging for at least 150 years.
Saturn, whose massive rings of ice and rock stretch out across a space as wide as the Earth is from the moon. While that’s well known, Fleisch notes this lesser known oddity: The planet’s density is so low that If there were only a bathtub big enough, Saturn could float in it. (Saturn could provide the tub’s ring.)
NEPTUNE AND THAT OTHER PLANET
The Planetary Society calls Neptune “the planet of fire and ice,” and Uranus “the planet of wind and ice.” It adds that Neptune’s unusual ice oceans have “temperatures likely reaching thousands of degrees.” Uranus is of interest for its rings, its unique sideways tilt and unsolved mysteries about its formation and the source of its water.
Neptune and Uranus also are interesting because they resemble planets commonly found in other stellar systems.
Really far out
Viewers should also stay tuned for news of exo-planets being found in other stellar systems and potentially in other galaxies. Planet-hunters look for signs of them in:
1. Dark dots traveling across the surfaces of stars.
2. Stars with slight wobbles that may be due to a planet’s gravitational pull.
3. Places where the presence or remains of past civilizations can be seen.
4. Radio waves with characteristics that don’t tend to occur naturally or that resemble the signals that humans produce.
“We’ve discovered almost 6,000 exo-planets in the last 30 years,” Fleisch said, “and it’s likely that most of the hundreds of billions of stars in our Milky Way Galaxy have planets, not to mention that stars in the hundreds of billions of galaxies in the known Universe.”
As scientists search for signals from other civilizations, “all of our FM radio and television signals” are being broadcast out into space.
Which means that Gomer Pyle, Ellie Mae Clampett and Aunt Bee may be humanity’s first intergalactic ambassadors, while Spock spreads his fingers and encourages others to “live long and prosper.”