Starts With a Bang! 21 May 2019, 14:01 UTC Imagine the early days of our Solar System, going back billions of years. The Sun was cooler and less luminous, but there were (at least) two planets — Earth and Mars — with liquid water covering large portions of their surfaces. Neither world was completely frozen over owing to the substantial presence of greenhouse gases, including carbon dioxide. Both may have even had primitive life forms in their young oceans, paving the way for a bright, biology-friendly future. Over the past few billion years, both planets have undergone dramatic changes. Yet, for some reason, while Earth became oxygen-rich, remained temperate, and saw life explode on its surface, Mars simply died. Its oceans disappeared; it lost its atmosphere; and no life signs have yet been found there. There must be a reason why Mars died while Earth survived. It took decades, but science has finally figured it out.
Bad Astronomy 21 May 2019, 13:00 UTC Mars has fascinated humans for, well, forever. A bloodshot, baleful eye in the heavens… telescopic observations furthered its allure, with straight lines across the surface that looked like canals, and barely glimpsed features that changed with season, hinting at perhaps Earth-like conditions.
Scientific American 21 May 2019, 12:00 UTC Space, as Douglas Adams so aptly put it, is big. Compared with the confines of our own planet, the solar system’s expanse is absurdly huge. Yet a recent study suggests that at current growth rates, humanity could practically exhaust the most accessible riches in our stellar neighborhood within less than five centuries.
Astro Bob 20 May 2019, 20:19 UTC When you travel east or west of your home it only affects the rising time of the stars. If you live in Iowa and fly to Baltimore the stars rise an hour earlier. It gets dark there an hour sooner. Fly to Utah, and it gets dark an hour later. Otherwise observers in both places see the identical stars. But if you travel north or south of your home, which stars you see changes. Even driving 1o0 miles (160 km) makes a difference but too subtle for most of us to notice.