Preparing to explore the surface of the Moon goes well beyond designing and building safe spacecraft and spacesuits. NASA also has to ensure the surface vehicles and suits have the mobility required to do science, and that astronauts have the tools they need to identify and scoop up rock and soil samples. Additionally, NASA astronauts are trained in geology, spending countless hours practicing doing science at locations on Earth that resemble regions they might see on the Moon. All this is done in an effort to establish a long-term presence on the Moon and to help answer some outstanding science questions about the history of Earth and of the solar system.
Video credit: NASA’s Goddard Space Flight Center/James Tralie (ADNET): Lead Producer, Lead Editor/Lonnie Shekhtman (ADNET): Lead Writer/Kelsey Young (NASA/GSFC): Scientist/Trevor Graff (Jacobs Technology): Scientist/Aaron E. Lepsch (ADNET): Technical Support/”Saana” and “Seasons” by Torsti Juhani Spoof from Universal Production Music
A near-Earth object (NEO) is any small Solar System body whose orbit brings it to proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). If a NEO’s orbit crosses the Earth’s, and the object is larger than 140 meters (460 ft) across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but a small fraction are comets.
There are over 20,000 known near-Earth asteroids (NEAs), over a hundred short-period near-Earth comets (NECs), and a number of solar-orbiting spacecraft and meteoroids large enough to be tracked in space before striking the Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of the Earth. NEOs have become of increased interest since the 1980s because of greater awareness of the potential danger. Asteroids as small as 20 m can damage the local environment and populations. Larger asteroids penetrate the atmosphere to the surface of the Earth, producing craters if they impact a continent or tsunamis if they impact sea. Asteroid impact avoidance by deflection is possible in principle, and methods of mitigation are being researched.
Two scales, the Torino scale and the more complex Palermo scale, rate a risk based on how probable the orbit calculations of an identified NEO make an Earth impact and on how bad the consequences of such an impact would be. Some NEOs have had temporarily positive Torino or Palermo scale ratings after their discovery, but as of March 2018, more precise calculations based on longer observation arcs led in all cases to a reduction of the rating to or below 0.
Since 1998, the United States, the European Union, and other nations are scanning the sky for NEOs in an effort called Spaceguard. The initial US Congress mandate to NASA was to catalog at least 90% of NEOs that are at least 1 kilometre (0.62 mi) in diameter, which could cause a global catastrophe,and had been met by 2011. In later years, the survey effort has been expanded to smaller objects which have the potential for large-scale, though not global, damage.
Measurements from NASAs Transiting Exoplanet Survey Satellite (TESS) have enabled astronomers to greatly improve their understanding of the bizarre environment of KELT-9 b, one of the hottest planets known. Located about 670 light-years away in the constellation Cygnus, KELT-9 b was discovered in 2017 because the planet passed in front of its star for a part of each orbit, an event called a transit. Transits regularly dim the stars light by a small but detectable amount.
Between July 18 and Sept. 11, 2019, as part of the mission’s yearlong campaign to observe the northern sky, TESS observed 27 transits of KELT-9 b, and these observations allowed the team to model the systems unusual star and its impact on the planet. KELT-9 b is a gas giant world about 1.8 times bigger than Jupiter, with 2.9 times its mass. Tidal forces have locked its rotation so the same side always faces its star. The planet swings around its star in just 36 hours on an orbit that carries it almost directly above both of the star’s poles.
The close orbit means the planet’s dayside temperature is around 7,800 degrees Fahrenheit (4,300 C), hotter than the surfaces of some stars. This intense heating also causes the planets atmosphere to stream away into space.
Its odd host star is about twice the size of the Sun and averages about 56 percent hotter. But it spins 38 times faster than the Sun, completing a full rotation in just 16 hours. Its rapid spin distorts the stars shape, flattening it at the poles and widening its midsection. This causes the stars poles to heat up and brighten while its equatorial region cools and dims, a phenomenon called gravity darkening. The result is a temperature difference across the stars surface of almost 1,500 F (800 C).
With each orbit, KELT-9 b twice experiences the full range of stellar temperatures, producing what amounts to a peculiar seasonal sequence. The planet experiences summer when it swings over each hot pole and winter when it passes over the stars cooler midsection. So KELT-9 b experiences two summers and two winters every year, with each season about nine hours.
KELT-9 b begins its transit near the star’s bright poles, and then blocks less and less light as it travels over the star’s dimmer equator. This asymmetry provides clues to the temperature and brightness changes across the stars surface, and they permitted the team to reconstruct the stars out-of-round shape, how its oriented in space, its range of surface temperatures, and other factors impacting the planet.
The sky crane system lowers the rover with a 7.6 m (25 ft) tether to a soft landing—wheels down—on the surface of Mars. This system consists of a bridle lowering the rover on three nylon tethers and an electrical cable carrying information and power between the descent stage and rover. As the support and data cables unreel, the rover’s six motorized wheels snap into position. At roughly 7.5 m (25 ft) below the descent stage the sky crane system slows to a halt and the rover touches down. After the rover touches down, it waits two seconds to confirm that it is on solid ground by detecting the weight on the wheels and fires several pyros (small explosive devices) activating cable cutters on the bridle and umbilical cords to free itself from the descent stage. The descent stage then flies away to a crash landing site 650 m (2,100 ft) away.
In 2017, NASA’s Hubble Space Telescope captured an image of a huge wing-shaped shadow cast by a fledgling star’s unseen, planet-forming disk. The young star, called HBC 672, is casting the shadow across a more distant cloud in a star-forming region—like a fly wandering into the beam of a flashlight shining on a wall.
Video credit: NASA’s Goddard Space Flight Center/Paul Morris (USRA): Producer / Editor/Visualization Credit: NASA, ESA, and A. James and G. Bacon (STScI)/Jason Steele [ ASCAP ]/Soundcast Music [ SESAC ] and Universal Production Music.
As of June 2020, NASA’s Solar Dynamics Observatory — SDO — has now been watching the Sun non-stop for over a full decade. From its orbit in space around the Earth, SDO has gathered 425 million high-resolution images of the Sun, amassing 20 million gigabytes of data over the past 10 years. This information has enabled countless new discoveries about the workings of our closest star and how it influences the solar system.
With a triad of instruments, SDO captures an image of the Sun every 0.75 seconds. The Atmospheric Imaging Assembly (AIA) instrument alone captures images every 12 seconds at 10 different wavelengths of light. This 10-year time lapse showcases photos taken at a wavelength of 17.1 nanometers, which is an extreme ultraviolet wavelength that shows the Sun’s outermost atmospheric layer — the corona. Compiling one photo every hour, the movie condenses a decade of the Sun into 61 minutes. The video shows the rise and fall in activity that occurs as part of the Sun’s 11-year solar cycle and notable events, like transiting planets and eruptions.
While SDO has kept an unblinking eye pointed towards the Sun, there have been a few moments it missed. The dark frames in the video are caused by Earth or the Moon eclipsing SDO as they pass between the spacecraft and the Sun. A longer blackout in 2016 was caused by a temporary issue with the AIA instrument that was successfully resolved after a week. The images where the Sun is off-center were observed when SDO was calibrating its instruments.
Video credit: NASA’s Goddard Space Flight Center/SDO/Scott Wiessinger (USRA): Lead Producer/Tom Bridgman (GST): Lead Data Visualizer/Mara Johnson-Groh (Wyle Information Systems): Lead Science Writer/Lars Leonhard
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