Issue No. 18

The Orbital Index

Issue No. 18 | Jun 25, 2019

🚀 🌍 🛰️

Mars made a gaseous emission this week. The red planet released its largest puff of methane to date. Curiosity measured 21 parts per billion of atmospheric methane last Wednesday with its SAM instrument, tripling a previous high reading of 7 ppb in 2013. Mars seems to have a seasonal methane cycle (and this measurement fits that cycle), but it is unclear whether the source of summer peaks is abiotic, microbial, or thermogenic (past microbial). Previous measurements were of such trace amounts that Curiosity was unable to perform isotope analysis which can help indicate the source. We hope the higher concentrations detected last week make analysis possible, although it will be nowhere near definitive. ESA’s ExoMars Trace Gas Orbiter also passed over Curiosity’s location and may corroborate results derived from the rover’s instruments. The conversation around evidence for life on Mars has a long history going back to the 1976 Viking landers’ labeled release (LR) experiment. Here’s a 2015 video of the Viking LR principal investigator surveying available evidence for life on Mars.

Two temperate Earth-sized planets have been spotted in the habitable zone of a star 12.5 light years away [paper]. In terms of habitability, it’s possible, but don’t get your hopes up. The tidally locked planets orbit the calm red dwarf Teegarden, a star with 1/10 the mass of our Sun that is so faint that it was only discovered in 2003, despite its closeness. Its eventual discovery was due to its large proper motion. Teegarden, and presumably its planets, are ~8 billion years old, roughly twice as old as our solar system (e.g. there has been plenty of time for life to evolve, invent Facebook, and wipe itself out). The planets were detected through the radial-velocity method: by watching how the star moves as it orbits its planetary system’s shared center of mass. We have now detected a total of 52 potentially habitable exoplanets and 4003 exoplanets in total, many of which are of classes we hadn’t known were possible, such as hot Jupiters and super-Earths. Related: visual art inspired by TRAPPIST-1, another red dwarf exosolar system with 7 planets, and 3 in the habitable zone.

A new, tentative schedule has surfaced for Commercial Crew launches later this year. The preliminary new schedule preserves the possibility of both Boeing and SpaceX launching humans into orbit before their end of year targets. Boeing’s Orbital Flight Test (OTF) is scheduled for mid-September, with SpaceX’s manned DM-2 then scheduled for a 7-day mission in mid-November, and immediately followed by Boeing’s Crew Flight Test (CTF) for 10 days at the beginning of December. No update yet on SpaceX’s in-flight abort test which is awaiting a replacement Crew Dragon vehicle.


  • New simulational research [paper] suggests that our young Sun rotated more slowly than half of stars its age, and that charged particles from such a slow-rotating young star could strip potassium and sodium from the lunar regolith, resolving the unexplained difference in the occurrence of these elements on the Moon vs in the Earth’s crust; additionally, the Sun’s slow early rotation is supported by our own existence—rapidly-rotating stars often have “super flares” that wouldn’t have been so good for life.
  • Water droplets in clouds need something to form around, which is usually dust or salt on Earth, but simulational research [paper] suggests that high Martian clouds are seeded by “meteoric smoke” (dust from vaporizing meteorites), which we have also detected in high noctilucent clouds at the Earth’s poles.

News in brief. NASA’s OSIRIS-REx took the closest image ever taken from an orbiting spacecraft last week when it entered a bound circular 680m orbit of Bennu; ESA signed a launch contract with Arianespace to launch the Jupiter Icy Moons Explorer (Juice) in 2022 on a 7.5-year flight to the Jovian system where it will study Jupiter, Ganymede, Europa, and Callisto; Blue Origin test fired (video) their BE7 lunar lander engine for the first time; and, the ESA also announced a new mission, called the “Comet Interceptor”, that comprises three spacecraft that will loiter together at the (increasingly crowded) L2 Lagrange point until a suitable comet wanders in from the Oort cloud or another “Oumuamua-like interstellar object” is spotted, then the trio will speed to meet the object as it comes into the inner solar system for the first time.


Falcon Heavy streaks into the Florida night sky carrying STP-2

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