Early May at 5:30 AM looking southeast

Sunday, May 1, 2022

The National Academies of Sciences recently released its Planetary Sciences and Astrobiology Decadal Survey that covers the priorities for the development planetary science missions for NASA and NSF for 2023-2032. Since it takes roughly ten years for a mission to go from the drawing board to construction, it'll be in the latter part of the 2030s before these missions would launch (and then many months to years before the spacecraft would reach their target). 

The Decadal Survey outlines the research topics for three classes of NASA missions: large expensive flagship missions and lower cost New Frontiers missions and Discovery missions, with the New Frontiers missions being about twice as expensive as the Discovery-class missions. The top-priority flagship mission will send an orbiter to Uranus that would be similar to the Cassini mission that orbited Saturn for 13 years. The Uranus mission will include a probe into Uranus' atmosphere. Uranus has been visited only once when Voyager 2 flew by in 1986. Most of what we know about Uranus comes from that brief flyby. Planetary alignments for getting to Uranus using a gravitational assist from Jupiter will be right between 2031 and 2038.

The next highest priority flagship mission is an orbiter-lander mission to Saturn's moon Enceladus which we believe has an ocean of water below its icy surface. Enceladus has geysers shooting material up hundreds of miles above the surface through large cracks near its south pole. Sampling of the geyser material by Cassini found salts (sodium chloride and potassium chloride) and carbonates mixed in with the water. That means the liquid water layer is in contact with the rocky core instead of being sandwiched between ice layers. If there is an ocean below the icy surface, Enceladus could be another place to look for life besides Mars and Jupiter's moon, Europa.

Europa will be visited later this decade by the Europa Clipper mission that should launch in 2024 and arrive at Jupiter in 2030. The Europa Clipper mission was a high-priority mission of the previous decadal survey. While orbiting Jupiter, the Europa Clipper will fly by Europa at least 45 times up close. Like Enceladus, Europa has a liquid water layer below its icy surface that contains more water than all of Earth's oceans and rivers combined. 

Europa is criss-crossed with a number of double-ridge crack features that are very similar to a recently-discovered double-ridge feature in Greenland. The double-ridge feature in Greenland formed when a pressurized liquid water pocket in the ice layer cracked the surface and the water rose up to fill the crack. That water in the crack refroze fracturing the ice that flanks the central frozen conduit. Much of the remaining water in the subsurface pocket then rose up through those secondary cracks to form the symmetric ridges on either side of the central conduit. If Europa's double-ridge crack features form in the same way, the ice layer would need to be just a few miles thick and the formation process provides a way to transport organic compounds between the surface and the deep liquid water ocean below. 

The New Frontiers missions will focus on the following topics: a Centaur asteroid orbiter/lander,  a sample return from dwarf planet Ceres, a sample return from a comet, a lunar geophysical network, a Saturn atmosphere probe, an orbiter of Saturn's largest moon Titan, a Venus explorer either on the surface or floating in the clouds, and maybe a mission to Neptune's large moon Triton.

The Decadal Survey also recommends enhancing work on detecting, tracking, and characterizing near-Earth objects and how to deflect ones 140 meters or larger that could hit Earth in the future. Another section of the Decadal Survey report focuses on the diversity, equity, inclusivity, and accessibility of the planetary science enterprise. A broader, more diverse population of scientists and engineers will ensure the United States' leadership in innovative space exploration. See https://www.nationalacademies.org/news/2022/04/report-identifies-priority-planetary-science-missions-planetary-defense-efforts-and-strategic-investments-for-the-next-decade for more details. 

In the more immediate future, early morning risers will be able to see the four bright planets Venus, Jupiter, Mars, and Saturn, in the eastern sky. This morning Venus and Jupiter were right next to each other about a pinky width at arm's length apart. Over the rest of May you'll see Jupiter and Mars draw closer and closer together for their May 29 conjunction. 

The peak of the Eta Aquariid meteor shower will be the night of May 5/6 but it has a broad peak of a few nights on either side of the peak. The Eta Aquariids are the result of Earth passing through the dust trail left behind by Comet Halley. The moon will be at just waxing crescent during that time, so it won't interfere that much on the nights leading up to the peak and the night of the peak. 

The moon was at new moon phase yesterday, April 30, so it'll be at full phase half a month later, or May 15. This full moon will be directly behind Earth with respect to the sun, so the moon will pass through Earth's shadow for a total lunar eclipse. Fortunately, this will happen in the early evening after sunset—totality will run from 8:29 to 9:54 PM

I hope you'll be able to enjoy a truly dark sky filled with stars sometime this month!

Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com