The daylight is relentless and scorching. But the orientation produces a rather cool phenomenon. “It lets Mercury have regions of permanent shadow near its poles that are never sunlit, and lets ice be present in those regions—even on the planet closest to the sun,” says Nancy Chabot, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory.
“It’s one weird little planet,” Byrne adds.
“There is no springtime on Venus, nor any other season—no seasons in hell!” says Allan Treiman, a scientist at the Lunar and Planetary Institute.
It’s difficult to sugarcoat the environment on Venus. Surface temperatures are a sizzling 870 degrees Fahrenheit (470 degrees Celsius), hot enough to melt lead, all year round. Like Mercury’s, Venus’s axis isn’t tilted enough to produce a noticeable difference.
But the real reason the planet doesn’t have any seasons is its atmosphere, which is choked with clouds. “The clouds are so thick that its surface gets nearly no light or heat from the sun. Nearly all the sunlight and heat are absorbed by clouds, which then radiate heat down to the surface—the famous greenhouse effect,” Tremain says. “Venus clouds circulate faster than the surface does, so all the greenhouse heat is spread around the planet, whether it’s day or night.”
That’s not all. “To top everything else off, Venus’ day is longer than her year,” says Vicki Hansen, a scientist at the Planetary Science Institute. (It takes 243 Earth days for Venus to rotate once on its axis, but 225 Earth days for the planet to loop around the sun.) “So if she had spring, it would be hard to say what day it happened.”
Mars’s axis is tilted slightly more than Earth’s—about 25 degrees—which means the planet experiences distinct seasons, too. In fact, like the Northern hemisphere here, the Northern hemisphere on Mars is entering spring now.
“The Northern hemisphere is starting to heat up; the Southern hemisphere cooling off—just like on Earth,” says Don Banfield, a scientist at the Cornell Center for Astrophysics and Planetary Science.
Well, not just like on Earth. Orbits affect seasons, too; the Martian year is twice as long as a terrestrial year, so the seasons stretch out longer. There are seasonal trends, such as summer dust storms, “but without rain and plants, they aren’t quite as obvious,” says Banfield.
“Jupiter does not have a springtime,” says Cheng Li, a scientist at NASA’s Jet Propulsion Laboratory. Like Mercury, Jupiter’s axial tilt is too small to matter.
Saturn does have spring: Its axial tilt is similar to that of Earth and Mars.
“Saturn is warm in the summer and cold in the winter,” says Leigh Fletcher, a planetary scientist at the University of Leicester. “The clouds and chemicals respond to these changes in sunlight. Perhaps the best example is the color of Saturn’s atmosphere, which shifts from blue hues in the winter—relatively clear skies with very few hazes—to golden hues in summer—a more smoggy atmosphere with lots of hazes.”