Recently, I was a guest on the Forum talk show on the San Francisco Bay Area public radio station, KQED, and got a chance to talk about astronomy news, what can be seen in the sky this summer, and the anticipation we all feel waiting for the first images from the James Webb Space Telescope. You can hear the 15-minute interview at: https://www.kqed.org/forum/2010101889700/celestial-events-abound-in-julys-night-skies
Among the news items we discussed is the one shown in the accompanying image. The Perseverance Rover on Mars has been exploring Jezero Crater, where it landed. We believe this crater was full of water billions of years ago and was fed by an active river on the surface of Mars. (In those early days, Mars had a much thicker atmosphere and warmer temperatures, so water could flow freely on its surface.) Now the rover (with scouting help from the little helicopter it brought along) has reached the delta that the river built up at its entrance to the crater. And, it is now seeing “sedimentary rock formations” — layers of material built up by flowing water, just as you would expect from a delta region not that different from the Mississippi River delta on Earth.