# The Orbital Index

Issue No. 104 | Feb 17, 2021

🚀 🌍 🛰
 ¶Tianwen takes another step. China’s first interplanetary mission successfully arrived at Mars last week, entering a highly elliptical 400 x 180,000 km orbit after a 15-minute deceleration burn. With this achievement, China became the sixth nation to orbit the Red Planet. Tianwen-1 (pronunciation guide) could become the first successful mission to deploy both an orbiter and rover from a single package, making it a very ambitious first solo deep-space mission for China. The orbiter will circle Mars until May, surveying the selected landing site in Utopia Planitia with as high as 50 cm/pixel optical imaging—this is the same region where Viking 2 landed and is thought to contain abundant buried ice. The solar-powered rover, similar in design to NASA’s Spirit and Opportunity rovers, but about a third larger at 240 kg, will be released for a retropropulsive landing once the site passes inspection. China is leaning heavily on its lunar robotic mission experience and has packed 13 scientific instruments into Tianwen-1. These surface and orbital instruments will study Martian morphology, regolith composition, ionosphere, magnetic field, and image the planet in high resolution. The orbiter and rover each have roles to play in every one of the mission’s primary science objectives, making it a unique look at orbiter- versus rover-based science (paper). The overarching focus is the history of water on Mars and its current presence as ice, both at the poles and in subsurface locations. Subsurface mapping will be conducted with regolith-penetrating radar from both the orbiter and rover, imaging up to 100 m below the surface and building on Yutu-2's success using the same technique on the Moon (the radar’s resolution will offer centimeter-level detail at up to 10 m depth, 1-meter detail at up to 100 m, and ice detection as deep as 1 km). With Tianwen's arrival, there are 10 missions currently operating at Mars—from ESA (Mars Express, ExoMars Trace Gas Orbiter), ISRO (Mars Orbiter Mission), NASA (Mars Odyssey, Mars Reconnaissance Orbiter, Curiosity, MAVEN, Insight), Roscosmos (ExoMars Trace Gas Orbiter in collaboration with ESA), U.A.E. (Hope), and now China.
 Tianwen-1 took a picture of itself in deep space on its way to Mars with a deployable camera—which communicated with the main craft via wifi.
 ¶Seven minutes of terror. On Thursday, the largest and most ambitious of the 2020 Mars missions arrives. NASA’s Perseverance rover (and helicopter Ingenuity) will hit the Martian atmosphere traveling at 20,000 km/h and traverse the “seven minutes of terror” from interplanetary transfer to sitting alone in Jezero Crater at 3:55 pm EST—here’s an EDL (Entry, Descent, and Landing) trailer showing the complex progression which employs a supersonic parachute, autonomous guidance, and a rocket-powered sky crane. You can also watch an EDL visualization in your browser and read about how it will use Terrain Relative Navigation to find a safe landing spot. The landing show and virtual NASA Social start at 11:15 a.m. PST / 2:15 p.m. EST on this Thursday (the Empire State Building and Krispy Kreme will be lit for the event 🍩). Perseverance is phenomenally complex, its Sample Caching System alone contains 3,000+ parts and two robotic arms. We’re excited for all the sciencing this nuclear-powered, sample-drilling, laser-zapping behemoth can do when it joins its friends on the only planet (known) to be inhabited solely by robots. 🤞
 Hope’s first image of Mars arrived this week, and it’s a lovely one.
 ¶Papers (about Mars, natch).The NOMAD instrument on ESA’s ExoMars Trace Gas Orbiter has failed to find evidence of methane in Mars’s mid-to-upper atmosphere, with a sensitivity down to 0.06 ppb (paper). This is interesting because ESA’s Mars Express orbiter (10 ppb) and Curiosity (21 ppb spike at the surface) both detected intermittent, seasonal puffs of methane on Mars. Whatever the geophysical or biogenic cause, Mars’ methane appears to be localized and intermittent. Related: Why methane is a likely biosignature in exoplanet atmospheres (paper).Unlike water, another planetary component that is essential for habitability is less obvious: long-lived radioactive elements (paper). Heating from the radioactive decay of thorium and uranium drives Earth’s geodynamo convection that powers plate tectonics and is probably essential to a protective magnetic field. Radioactive decay may also have been the source of Mars’s early climate. Newly formed planets can inherit differing amounts of these elements based on the compositions of their planetary nebulae. “With more radiogenic internal heating, the planet [...] has much more volcanic activity, which could produce frequent mass extinction events. On the other hand, too little radioactive heat results in no volcanism and a geologically ‘dead’ planet.” Somewhat unsurprisingly, our Sun falls in the middle of the range for occurrence of radioactive elements, with some stars having either twice or half as much. (Does this mean Musk’s “Nuke Mars” campaign is a good idea? Nope.)Based on oxidation of the very old components of a Martian meteorite (paper), there is evidence that Mars’ water (and by extension Earth’s) may have been part of the planet right after formation, as opposed to having been delivered by comets and asteroids later, as current theories suggest. If so, this could mean that most rocky planets have water, at least at some point in their life cycle.Based on the study of sedimentary mudstone at Gale Crater by Curiosity, scientists have determined that early Mars was colder than we thought, although still often above freezing (paper). The best analog on Earth, according to samples taken from all over our home planet, is Iceland.
 A sedimentary plain in Iceland may resemble the landscape near Gale Crater on Mars 3 billion years ago.
 ¶News in brief. Axiom Space raised $130 million—they are continuing to work on their ISS modules and have a private ISS mission that could launch as soon as January; a SpaceX Falcon 9 delivered 60 more Starlink satellites, but lost its 6x launched booster on landing (breaking their streak of 24 consecutive landings)—the next, and 20th, Starlink mission is planned for this coming Sunday; Lockheed Martin selected California-based ABL Space Systems to (attempt to) launch the first orbital rocket from the UK in 2022; NASA may buy one more Soyuz seat to the ISS for April; Russian Progress 76P MS-15 (intentionally) burned up after leaving the ISS; and, Turkish president Erdogan announced a 10-year space program, including lunar missions and the launch of a Turkish astronaut—the announcement was accompanied by the brief appearance of (soldiers standing around) a 3m high metal monolith near a UNESCO site. 🤷  A beautiful shot from orbit of Progress 76P MS-15 as it burned up in the atmosphere after leaving the ISS (photo by JAXA astronaut Soichi Noguchi).  ¶Etc.So how much will Perseverance really cost? About as much as the US department of defense spends every 33 hours; or, what Google makes in 6 days. An Up-Close Look At The First Martian Helicopter.Mars InSight will be listening for the impacts of two 77 kg Cruise Mass Balance Devices (is this what NASA calls ‘weights’?) released by Perseverance as it hits the atmosphere in order to adjust the descending spacecraft’s center of mass. These devices will lithobrake into Mars’ surface at 14,000 km/hr (paper), providing useful calibration data for the InSight team. (InSight’s SEIS seismometer is a marvel: “We have been able to detect, at about 10 hertz, displacement of the ground of the order of less than 5 picometers…which is a fraction of the size of an atom.”)Using GNU Radio to decode Mars 2020’s telemetry, which apparently includes a quote from Wernher von Braun (the father of American rocketry, and a Nazi).An opinion piece suggesting that for both physiological and psychological reasons, the first trip to Mars should be crewed by women.GHGSAT’s Hugo, launched on Transporter-1, has returned its first image of a methane plume. Methane is a potent greenhouse gas, with ~84x the impact of CO2 for 20 years after emission. We wrote about methane tracking from space in last year’s climate-focused issue.NASA launched a Deep Space Food Challenge to seek “ideas for novel food production technologies or systems that require minimal resources and produce minimal waste, while providing safe, nutritious, and tasty food for long-duration human exploration missions.” U.S. citizens can win up to$500k with novel lunar and Martian cooking research.Looking for life on Mars: Patricia Straat reflects on the divisive findings of Viking’s microbe-detecting Labeled Release experiment. Radio.garden (note: uBlock Origin was breaking this site for us, so you may need an incognito window.)Images of airbag prints and hearts on Mars. ❤️
 ¶Jobs.ESA’s Young Graduate Trainee program has applications open until March. Recent graduates with a Masters can apply to work on ESA missions.There are two open Satellite Operations Engineer positions at ESOC in Darmstadt, Germany on the Cluster mission. Email a CV to artur.scholz@esa.int if you are interested.
 A dust devil on Mars, caught by one of Curiosity’s navigation cameras on Aug. 9, 2020.