Sunsets On Mars Are Blue
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Yes, scientists can confirm, they are blue, and they occur in short intervals. They are the closest thing to a phenomenon we can see on the Red Planet.
The fact they exist is mostly because of how the sunlight hits the surface of Mars. Sunlight on the other planet passes through an atmosphere very different from Earth’s. That combination of the atmosphere and the surface means that the sunbeams hitting the surface get refracted, just as they would on Earth.
The result is a view of the surface as if it were at night. On Mars, it’s blue.
“If you go outside on a clear night here in Atlanta, you’ll see the city twinkle and you’ll see street lights turning on,” said Michael Smith, associate director of research at NASA’s Ames Research Center. “It’s the same phenomenon that happens on Mars, but it’s very, very dim, and the night sky is a million times fainter.”
The sunsets are one of the strongest and most readily accessible signs of an active atmosphere, not just an absence of one. Without an atmosphere, an uninhabited planet would be the dull brown of the moon — or, perhaps, of a post-apocalyptic “Mars: The Year One” novel.
Mars, however, still has some of the features we associate with a terrestrial planet — craters, dunes, and mountains — and even has some vegetation. But it is no Earthling paradise.
“I get the sense that people on Earth when they think about the landscape of Mars, they think about bleakness and death and despair,” said Zurbuchen, who leads NASA’s science missions. “But this is very different than that. The planet looks healthy. It looks green, and it looks alive.”
Satellites provide the most reliable data on the Martian atmosphere, with estimates that date back to the 1980s. It is thought to be about 100 times thinner than Earth’s atmosphere, and a little more than 1 percent as dense. It’s composed mostly of carbon dioxide, with traces of methane, oxygen, hydrogen, nitrogen, oxygen, sulfur, carbon monoxide, and maybe even carbon dioxide gas.
Samples returned from the Curiosity Rover, for example, have shown the environment was once comfortable for microbial life, with the right chemistry to support it. But it’s not as if no life ever existed on Mars. Liquid water appears to have pooled on the planet’s surface in the past, including in rivers and lakes.
Even so, scientists remain uncertain about the makeup of the planet’s atmosphere, which is a bit mysterious. There is a chemical called tholin, which was once thought to be an atmosphere-breaking substance. But scientists realized recently that it does not seem to exist in Mars’ atmosphere, meaning it was probably never there.
An analysis of Martian meteorites shows that the planet used to be a lot warmer than it is today. The rocks suggest that as the climate cooled, the Martian atmosphere became denser and lost its haze. As the atmosphere thinned, the temperature cooled, too. This downward spiral would have affected global conditions, including temperature and winds, which were the main drivers of weather and climate, said Dr. Jay Melosh, a planetary scientist at Purdue University.
“It would change how sunlight would be delivered to the surface, and you’d see drier conditions,” he said. “But there are places that would have been wetter.”
Now that we know there was once water on Mars, scientists say that, given the right conditions, it could possibly exist today. And if it does, it could exist in places where the rover has found seasonal streams and small waterfalls.
NASA’s Phoenix spacecraft found that rocks on the red planet carried a signature of water and that methane, a chemical that on Earth is often produced by living things, could be plentiful on Mars.
This is proof of Martian life, according to NASA. Scientists believe that if you took the amount of methane on the red planet and added it to the atmosphere on Earth, it would be about 10 times as strong as the greenhouse effect. The implication is that it could have been produced by living organisms.
Scientists do not know if these or other discoveries are proof of past life on Mars.
Some of the recent findings, however, have made this a central part of the exploration plan for the Mars 2020 rover, which will have instruments specifically designed to search for signs of past life.
Then, in the not-so-distant future, NASA and the European Space Agency plan to put a lander near the surface of the red planet, in search of organics — a life-friendly chemical that may have once been present on Mars and might be common in the universe. The prospect of finding life on Mars has driven much of the excitement surrounding this mission.
The Planetary Society, a nonprofit organization based in California, is working with scientists to encourage and fund the search for signs of life on Mars.
“I like to describe the lander as a telescope that can see much further out than the Hubble Space Telescope,” said Mitch Atkins, a former space science researcher and the CEO of the nonprofit. “And it’s not made of gold or diamonds, it’s made of titanium. And it will have a sensitivity that is 10,000 times greater than the Hubble Telescope.”
The next big milestone in the search for signs of life on Mars is to discover the environment that supports life, Atkins said. Until then, the only things to study are the more common — but no less puzzling — atmospheric gases, he said.
“Once we can identify the gases that are out there, then we can start to determine what kind of activity it’s producing and how much energy it’s taking in,” he said.
Melosh, too, is optimistic. After all, no one ever said finding life on Mars was going to be easy.
“It’s a great, great way to learn about the life,” he said. “If it’s anywhere, it’s on Mars. That’s why it’s exciting.”
Sadly, Dr. Melosh passed away in September of 2020. His work in this field has been groundbreaking and will compel future studies into this strange, but true phenomenon.
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