The Orbital Index

Eclipse highlights. Monday’s total solar eclipse was visible across sections of North America, with intermittent cloud cover disappointing some hopeful viewers. The Orbital Index team (Ben, Andrew, and Sarajane) were all able to make it to totality—and enjoyed the absolutely unique experience. Watchers may have noticed a solar prominence visible to the naked eye during totality. There were multiple smaller prominences also visible with magnification. Prominences are large plasma filaments that extend thousands of kilometers from the Sun’s surface—many times the Earth’s diameter—but stay anchored to the surface by a complex magnetic field (solar flares are similar, but are detached from the surface). While they occur regularly, often glowing red with the light of their superheated hydrogen, they are a treat to see in conjunction with an eclipse since, to be visible, they must be located such that they arc into space that’s outside the Moon’s coverage disc instead of toward, or away from, Earth. It helps that our Sun is currently heading into its solar maximum. Also visible were Venus (below and to the right) and Jupiter (up and to the left). Temperatures dipped by up to ~10 °C along the path of the eclipse. Here’s a cool video of the Moon’s shadow moving across the Earth composed of GOES-East stills, and another shot from a previously unrevealed (but speculated as existing) Starlink onboard camera. 

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NASA rover announcement. Last week, NASA announced three selections for the agency’s Lunar Terrain Vehicle Services (LTVS) contracts. The contract awards were to: Intuitive Machine’s Moon RACER (Reusable Autonomous Crewed Exploration Rover), Lunar Dawn from Lunar Outpost, and Venturi Astrolab’s FLEX rover. IM’s Moon RACER would be delivered on a Nova-D lander (Nova-C’s planned big sib) and developed as part of a group with AVL, Michelin, Boeing, and Northrop Grumman. Lunar Dawn (developed by Lunar Outpost in partnership with Lockheed Martin, MDA Space, General Motors, and Goodyear) will feature fully autonomous driving with or without crew on board. Meanwhile, Venturi Astrolab, who teamed up with Axiom Space and Odyssey Space Research, will continue development of its existing FLEX rover which has already been demonstrated at full scale in Death Valley (cf. Issues 160 & 214) and is scheduled for a test mission to the Moon’s surface on a ~2026 Lunar Starship demonstration. Skipped over in the selection process was Leidos, who partnered with NASCAR. The maximum value for the LTVS contracts is $4.6B over the next 13-15 years, but current contract sizes are relatively small—Intuitive Machines announced that theirs was $30M. This phase one contract covers a year-long period of system development and feasibility study. The final, fully developed rover, once selected, is scheduled to launch alongside Artemis V, which also features the first Blue Moon HLS lander. However, the LTVS requirements are for a rover with a lifespan of 10 years and the capability of continued remote science operation, in addition to Artemis crewed operations. This will be a challenging task given the lunar south pole’s harsh environment (ex. Nova-C didn’t reawaken after the lunar night, while SLIM, at mid-latitudes, has reawoken twice). NASA’s hope is that the LTVS rover will also eventually be used for commercial use—initially, NASA plans to take up 75% of the vehicle’s time, leaving 25% for commercial users, with the intention to shrink its usage as commercial demand grows. The LTVS contract does allow for additional selections and special “on-ramps” for added competition from other providers down the line. In roughly a year, remaining (or newly added) contractors will be awarded demonstration mission contracts to develop and deliver their rover(s) to the Moon for remotely controlled performance validation.

• A solar system with six hot gas giant planets in perfect resonance has been spotted (paper). The innermost planet does three orbits for every two of the next one out—a 3/2 resonance—which itself does three orbits for every two of the third planet, and so on for all four inner planets. The outer two planets are instead in a 4/3 resonance. This leaves the innermost planet completing six orbits for every 1 of the outermost—the whole system as 54:36:24:16:12:9. It’s a glorious dance. Most solar systems are thought to start in resonance, but only an estimated 1-in-100 retain it throughout their lives due to disruptions, such as from passing stars.
• Even very small collisions between space debris particles at orbital velocities should emit radiofrequency pulses detectable from the ground, potentially providing a new way to track currently untrackable clouds of dangerous micro-debris in orbit.
• The 6-km high concentric cliffs around Mars’ Olympus Mons may have started as contact zones where lava flows encountered an ancient ocean and were then later uplifted (paper). The solar system’s tallest volcano is thought to have formed due to a mantle hotspot, which unlike with Hawaiʻi or Yellowstone on Earth, formed one massive volcano instead of a volcanic chain due to Mars’ lack of plate tectonics.
• Relatedly, Mars may have seen volcanic activity quite recently—the Elysium Planitia region shows signs of large-scale lava flows and seismic activity as recently as 1 million years ago based on a detailed survey of MRO imagery and ground-penetrating radar measurements (paper). The survey found evidence of steam explosions and more than 40 volcanic events, the largest of which released 4,000 cubic kilometers of basalt. “Elysium Planitia was volcanically much more active than previously thought and might even still be volcanically alive today.” (Other recent studies suggest even more recent volcanism.)

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• NASA now knows what knocked Voyager 1 offline, but it will take a while to fix. Voyager 1’s remaining Flight Data Subsystem (its redundant copy failed in 1982) is the reason that the distant spacecraft is currently offline. Voyager’s FDS were the first computers on a spacecraft to use volatile memory. Unfortunately, one of Voyager 1’s FDS memory chips is malfunctioning—NASA hopes they can work around it, but it will likely take months.
• All about the hypothetical climates of tidally-locked exoplanets — “the popular perception of tidal-locked planets—hostile worlds split between a burning desert on the lit hemisphere, ice on the dark side, and, at best, a thin "twilight strip" of habitable temperatures in between, wracked by gale-force winds—is not a strictly impossible scenario in all its particulars, but our current best climate models predict (and have for quite some time now) that tidal-locked planets in the habitable zone with Earth-like atmospheres and quantities of surface water can more typically expect far more hospitable conditions, with comfortable temperatures and moderate prevailing winds across the lit hemisphere; that the hottest part of the planet will usually actually be the wettest; and that this habitable climate state may actually be more stable in some ways than that of a planet more like our own.” The whole blog is pretty amazing.
• Relatedly, LHS 3855b appears to be the first exoplanet that is convincingly tidally locked.
• Watch electricity flow through a wire a nanosecond at a time.