NASA's Perseverance Mars rover took a selfie with the Ingenuity helicopter, seen here about 13 feet (4 meters) away in this image from April 6, 2021, the 46th Martian day, or sol, of the mission. Perseverance captured the image using a camera called WATSON (Wide Angle Topographic Sensor for Operations and eNgineering), part of the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) instrument, located at the end of the rover's robotic arm.

NASA's 2001 Mars Odyssey spacecraft launched 20 years ago on April 7, making it the oldest spacecraft still working at the Red Planet. The orbiter, which takes its name from Arthur C. Clarke's classic sci-fi novel "2001: A Space Odyssey" (Clarke blessed its use before launch), was sent to map the composition of the Martian surface, providing a window to the past so scientists could piece together how the planet evolved.

The Perseverance rover has just landed on Mars. Meanwhile, its precursor Curiosity continues to explore the base of Mount Sharp (officially Aeolis Mons), a mountain several kilometers high at the center of the Gale crater. Using the telescope on the ChemCam instrument to make detailed observations of the steep terrain of Mount Sharp at a distance, a French-US team headed by William Rapin, CNRS researcher at the Institut de Recherche en Astrophysique et Planétologie (CNRS/Université Toulouse III/CNES), has discovered that the Martian climate recorded there alternated between dry and wetter periods, before drying up completely about 3 billion years ago.

Calibration and validation (CAL/VAL) is a key technology for quantitative application of space-borne remote sensing data. However, the complex space environment can cause many uncertainties and degrade calibration accuracy. In-flight calibration is always needed. The thermal emission of the Moon is stable over hundreds of years because there is no atmosphere and no significant physical or chemical change on its surface. The deep space view of the Microwave Humidity Sounder onboard NOAA-18 has viewed the Moon many times every year. Under solar illumination, the lunar surface shows stable and periodical variation in microwave brightness temperature (TB). The Moon is a potential calibration source for thermal calibration

The related work was published in Science China Earth Sciences as "Calibration of the space-borne microwave humidity sounder based on real-time thermal emission from lunar surface." Based on the heat conductive equation, the temperature profiles of lunar regolith at different regions and local time are simulated numerically with the real-time solar radiance and angle of incidence.