We’re lucky to have a neighbour like Venus, even though it’s totally inhospitable, wildly different from the other rocky planets, and difficult to study. Its thick atmosphere obscures its surface, and only powerful radar can penetrate it. Its extreme atmospheric pressure and high temperatures are barriers to landers or rovers.
It’s like having a mysterious exoplanet next door.
A team of astrophysicists has discovered a binary pair of ultra-cool dwarfs so close together that they look like a single star. They’re remarkable because they only take 20.5 hours to orbit each other, meaning their year is less than one Earth Day. They’re also much older than similar systems.
While the Earth absorbs a lot of energy from the Sun, a lot of it is reflected back into space. The sunlight reflected from Earth is called Earthshine. We can see it on the dark portion of the Moon during a crescent Moon. The Farmer’s Almanac said it used to be called “the new Moon in the old Moon’s arms.”
Earthshine is one instance of planetshine, and when we look at the light from distant exoplanets, we’re looking directly at their planetshine without it bouncing off another object.
If distant astronomers were looking at Earthshine the way we look at exoplanet shine, would the light tell them our planet is rippling with life?
Here’s a thorny problem: What if life doesn’t always appear on planets that can support it? What if we find more and more exoplanets and determine that some of them are habitable? What if we also determine that life hasn’t appeared on them yet?
Could we send life-bringing comets to those planets and seed them with terrestrial life? And if we could do that, should we?
The Curiosity rover has now reached its primary target on Mount Sharp on Mars, the mountain in the middle of Gale Crater the rover has been climbing since 2014. This target is not the summit, but a region over 600 meters (2,000 feet) up the mountain that planetary geologists have long anticipated reaching.
Known as the “sulfate-bearing unit,” the region is a boundary between the rocks that saw a lot of water in their history and those that didn’t; a possible shoreline, if you will. That boundary is already providing insights into Mars’ transition from a wet planet to dry, filling in a key gap in the understanding of the planet’s history.
Our Solar System contains eight planets and more than 200 moons. The large majority of those moons have no chance of being habitable, but some of them—Europa and Enceladus, for example—are strong candidates in the search for life.
Most stars will end their lives as white dwarfs. White dwarfs are the remnant cores of once-luminous stars like our Sun, but they’ve left their lives of fusion behind and no longer generate heat. They’re destined to glow with only their residual energy for billions of years before they eventually fade to black.
Could life eke out an existence on a planet huddled up to one of these fading spectres?