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Joe Palca

NASA tried a communications experiment with its latest mission to Mars, and it turned out spectacularly well.

On Nov. 26, as the probe known as InSight plummeted through the Martian atmosphere on its way to the planet's surface, two miniature spacecraft — known collectively as MarCO — relayed telemetry from InSight to Earth, assuring all those watching that the landing of the probe was proceeding successfully and was soft.

Updated at 7:37 a.m. ET Friday

Every two years or so, the sun, Earth and Mars line up — and that's what is happening now. It's a celestial orientation known as Mars opposition. Leaving aside any significance this might have for astrologers, from an astronomical point of view there's one thing you can say for sure about this Mars opposition: Mars will be brighter in the night sky than it's been for 15 years.

An Italian team of scientists says it has strong evidence of a subsurface lake of liquid water on Mars. It's a discovery that adds to the speculation that there could once have been life on Mars — and raises the possibility that it might be there still today, since liquid water is an essential ingredient for life.

NASA is building a new space telescope with astounding capabilities. The James Webb Space Telescope, scheduled for launch in 2018, will replace the aging Hubble Space Telescope and will provide unprecedented views of the first galaxies to form in the early universe. It might even offer the first clear glimpse of an Earth-like planet orbiting a distant star.

Hot tea on a hot day? Not for me, thank you. Not my idea of how to cool down.

Twenty-five years ago, an event occurred that is seared into the memory of most Americans: About a minute after liftoff, the space shuttle Challenger blew apart, killing all aboard, including teacher-astronaut Christa McAuliffe.

The day started off innocently enough. It was unusually cold in Florida that day, but NASA managers decided to attempt a launch anyway. As a subsequent investigation made clear, the cold temperature made O-rings, which were intended to contain hot gases, fail on the solid rocket boosters.