NASA’s More Accurate Eclipse Maps

A map showing the umbra (the Moon’s central shadow) as it passes over Cleveland at 3:15 p.m. local time during the April 8, 2024, total solar eclipse. (NASA SVS/Ernie Wright and Michaela Garrison)
NASA SVS/Ernie Wright and Michaela Garrison

For the 2017 solar eclipse, NASA published eclipse maps that took the irregular umbral shadow of the moon into account: the umbra is neither circular nor oval but irregular—more polygonal—thanks to the uneven topography and elevation of both the moon and the earth. Not accounting for that introduces errors into the map that could make the difference between observing a partial rather than a total eclipse. The process behind those more accurate eclipse maps, which involves computer processing of both lunar and terrestrial elevation models, has now been published in The Astrophysical Journal. [Bad Astronomy]

New Gravity Map of Mars Reveals Subsurface Variations

Gravity map of Mars. The red circles show prominent volcanoes on Mars and the black circles show impact crates with a diameter larger than a few 100 km. A gravity high signal is located in the volcanic Tharsis Region (the red area in the centre right of the image), which is surrounded by a ring of negative gravity anomaly (shown in blue).
Gravity map of Mars, from Root et al.

A study presented earlier this month at the Europlanet Science Congress maps the variations in Mars’s gravitational field.

Dr Root and colleagues from TU Delft and Utrecht University used tiny deviations in the orbits of satellites to investigate the gravity field of Mars and find clues about the planet’s internal mass distribution. This data was fed into models that use new observations from NASA’s Insight mission on the thickness and flexibility of the martian crust, as well as the dynamics of the planet’s mantle and deep interior, to create a global density map of Mars.

The density map shows that the northern polar features are approximately 300-400 kg/m3 denser than their surroundings. However, the study also revealed new insights into the structures underlying the huge volcanic region of Tharsis Rise, which includes the colossal volcano, Olympus Mons.

Abstract, press release, Universe Today.

Previously: New Gravity Map of Mars.

Better Lunar Mapping Through Semi-Automated Photoclinometry

A method to improve the accuracy of maps of the lunar surface was published last month in The Planetary Science Journal. Photoclinometry, also known as shape-from-shading, can dramatically improve the resolution of digital elevation models generated from Lunar Reconnaissance Orbiter data, but it’s apparently rather labour-intensive. From the Brown University press release: “The scholars outline in the study how advanced computer algorithms can be used to automate much of the process and significantly heighten the resolution of the models. The new software gives lunar scientists the tools to create larger maps of the Moon’s surface that contain finer details at a much faster pace, the researchers say.” [Universe Today]

Chinese Academy of Sciences Releases 1:2,500,000 Geologic Maps of the Moon

Chinese Academy of Sciences

Last month the Chinese Academy of Sciences released a set of geologic maps of the moon at 1:2,500,000 scale—twice the resolution of the USGS’s 1:5,000,000 scale maps. Available, it seems, as a geologic atlas as well as quadrangle maps—though it’s not immediately apparent from where. News: Nature, Popular Science, Universe Today.

xkcd: ‘Every Eclipse Path Map’

An xkcd cartoon about eclipse path maps.
Randall Munroe, “Every Eclipse Path Map,” xkcd, 17 Apr 2024.

Looks like we’re not quite done with eclipse maps, especially the whimsical sort, and it’s not at all invalid for xckd to have (what is probably going to be) the last word on the subject (at least for a while), with this fictional map showing the fictional path of a fictional eclipse over a fictional landscape, with rueful descriptions of fictional places where trying to see the fictional eclipse will come to a bad end for the fictional observers. (And you thought it was bad you got clouds.)

New Eclipse Map Claims Narrower Path of Totality

CNN: “New map calculations have raised some concerns that the path of totality—where it’s possible to see the moon completely block out the sun—is slightly narrower than NASA calculated. That means some cities on the edge of the route that were expecting to experience a second or two of total darkness might be left out.” The calculations were done by John Irwin, whose revised map can be found here. This page has the technical details, while Jamie Carter explains the implications: if Irwin’s correct, we’re talking about a literal edge case of a few hundred metres. Go further into the path of totality!

Previously: Cloud Cover Risk During the 2024 Solar Eclipse; Mapping Two Solar Eclipses.

Cloud Cover Risk During the 2024 Solar Eclipse

Eclipses aren’t any fun if you travel to go see one and it’s cloudy. I’ve been debating with myself what to do about next month’s total solar eclipse: the path of totality is a couple hours’ drive away and therefore manageable, but from what I’ve gathered the odds of clear skies aren’t great. These odds are based not on weather forecasts—still too early for that—but on historical data. For example, NASA Earth Observatory’s map, above, shows the average of the past 20 years of cloud cover across North America’s eclipse track on the day of the eclipse (April 8). Want more detail? Like, a lot more? See this incredibly detailed analysis from Eclipsophile’s Jay Anderson; I believe he’s a former meteorologist, and boy does it show in this piece. See also this Weather Underground article from last January, plus coverage from CBC News.

Previously: Mapping Two Solar Eclipses.

Astronomy Atlas 1899: A New Kickstarter Project

Banner image for the Astronomy Atlas 1899 Kickstarter project

Alejandro Polanco’s latest Kickstarter project, Astronomy Atlas 1899, does for 19th-century astronomy atlases what his previous Geography 1880 project did for school atlases of the era: create an anthology of the best maps, drawings and diagrams from the books available to him.

In my library, in addition to the collection of geographical atlases from the 18th to the 21st century, there is a whole series of old books on astronomy, and of all of them, the ones that attract me the most are those published between 1880 and 1930. This was a time when science was developing at an astonishing rate and astronomy was changing radically. […]

In total there are twelve astronomical atlases in this library, mostly Spanish, French and English, published between 1880 and the early 1930s. From these I have selected the most interesting engravings and drawings, arranged them chronologically and given details of the original source. I have also supplemented many of them with other engravings from the Biblioteca Nacional de España and similar sources.

Digital (€18), softcover (€45) and limited-edition hardcover (€90) versions will be produced.

Mapping Two Solar Eclipses

Map of the path of the annular eclipse on October 14, 2023, across the American Southwest.
Michael Zeiler, GreatAmericanEclipse.com

Two upcoming solar eclipses in North America—the annular eclipse on October 14, and the total eclipse on April 8, 2024—are the subject of numerous eclipse maps that track the path of totality and its duration along that path.

NASA’s Solar Eclipse Explorer currently focuses on this month’s annular eclipse, with paths of the 2017 and 2024 eclipse for comparison. [Maps Mania]

The Eclipse Company has separate maps for this month’s annular eclipse and next April’s total eclipse: these maps include data for locations along the path, including time, duration, the sun’s altitude and chance of clouds based on historical weather data. [PetaPixel]

The last time I went looking for eclipse maps, back in 2017, there was a website called GreatAmericanEclipse.com, which was the most recent of the websites showcasing the eclipse maps of Michael Zeiler. It’s still very much a going concern, with maps covering North America, individual U.S. states, and detailed maps of the path itself. These are static maps rather than the above interactive maps, but there are a lot of them, and not just for this month’s annular and next year’s total eclipse: there’s a fair bit of historical (and future!) eclipse maps there too.

Update 10:20 PM: Andy Woodruff’s scrolling map of the 2024 eclipse.

Previously: An Almost-Too-Late Roundup of Historical and Unusual Eclipse Maps; Mapping the August 2017 Solar Eclipse; Another Solar Eclipse Website; Michael Zeiler’s Solar Eclipse Map Website; Eclipse Maps.

The Moon in LEGO

A poster map of the Moon rendered in LEGO by Marc Sloan.
Marc Sloan (LEGO Ideas)

On the LEGO Ideas website, user-submitted projects that reach the 10,000-supporter level are evaluated by LEGO to determine whether it can become a shipping product. Which is to say that Marc Sloan’s 2,360-piece “The Moon: Earth’s Companion,” a Moon map poster rendered in LEGO, stands at least some chance of being something one could buy at some point. [Universe Today]

A Martian Mosaic at Five Metres per Pixel

Global CTX Mosaic of Mars (screenshot)

The Global CTX Mosaic of Mars, produced by CalTech’s Bruce Murray Laboratory for Planetary Visualization, is a 5.7-terapixel mosaic of the Martian surface at a resolution of five metres per pixel. The mosaic is available in a number of different formats (via ArcGIS Online, KML, shapefiles), as well as via this online viewer; and the Lab is quite transparent about how they constructed it from Mars Reconnaissance Orbiter Context Camera (CTX) data. [Maps Mania/La Cartoteca]

The Soviet Space Program’s Remarkable Electromechanical Navigation Device

Front-facing view of a Globus navigational device from a Soyuz capsule.
Ken Shirriff

You must see this. Ken Shirriff got his hands on an example of a navigational device from a Soyuz spacecraft and opened it up to see how it worked. Known as a Globus (its proper name is Индикатор Навигационный Космический—roughly, space navigation indicator), it’s an incredibly complicated marvel of gears and cams, an electromechanical analog computer that showed the capsule’s position on a physical globe. The position was predicted—the Globus received no navigational data. Ken’s got lots of photos of the innards at his website. See also his Mastodon thread. He has hopes of getting the thing operational, so keep an eye out for that.

(Based on the presence of NASA tracking sites on the globe, Ken thinks this particular unit was meant for the Apollo-Soyuz program, but I kind of wonder whether that was a function of the 1967 Rescue Agreement between the U.S. and the USSR instead.)

The Mercury capsule had something similar for a while: the Earth Path Indicator. One example sold for nearly $100,000 in 2019.

Large-Scale Geologic Maps of Mars

Geologic Map of Olympus Mons Caldera, Mars (USGS)
Geologic Map of Olympus Mons Caldera, Mars. USGS SIM 3470.

The USGS’s Astrogeology Science Center highlights three geologic maps of Mars released in late 2021. The maps are large-scale, focusing on specific Martian features (e.g. Olympus Mons, above).

Though maps have historically covered large areas, with crewed lunar missions on the horizon and other missions across the solar system in the planning stages, large-scale, small-area maps are starting to steal the limelight. These large-scale, small-area maps provide highly detailed views of the surface and allow scientists to investigate complex geologic relationships both on and beneath the surface. These types of maps are useful for both planning for and then conducting landed missions.

The maps are of Olympus Mons Caldera, Athabasca Valles and Aeolis Dorsa. Interactive versions, with toggleable layers over spacecraft imagery, are also available: Olympus Mons Caldera, Athabasca Valles, Aeolis Dorsa.

Mapping the Shoreline of an Ancient Martian Ocean

3D map showing evidence of ancient Martian shoreline
Benjamin Cardenas/Penn State (Creative Commons)

“A recently released set of topography maps provides new evidence for an ancient northern ocean on Mars. The maps offer the strongest case yet that the planet once experienced sea-level rise consistent with an extended warm and wet climate, not the harsh, frozen landscape that exists today.” Press release, video, article (JGR Planets). [Universe Today]