Active Volcano on Venus: Before and After Images

European Space Agency's infographic: 'Evidence for active volcanoes on Venus' (June 18, 2015)
European Space Agency’s 2015 infographic: “Evidence for active volcanoes on Venus”.

Venus is dead as a doornail as far as life is concerned. Life as we know it, at any rate, and already I’m drifting off-topic.

Geologically, though, we’ve known that there’s still metaphorical life in Venus. Or was, until very recently.

Orbiters have sent back evidence of geologically-recent volcanic activity, including images of shield volcanoes and lava flows.

But we had no direct evidence of a volcano that’s active now. Until scientists sifted through data recorded and stored in the early 1990s.

Observing Venus: Five Millennia in About 700 Words.

Schematic diagram of Peter Apian's (Petrus Apianus) cosmology, largely reflecting Aristotelian physics and cosmology. From Peter Apian's 'Cosmographia,' annotated by Gemma Frisius. (1524) Reproduced in Edward Grant's 'Celestial Orbs in the Latin Middle Ages.' (1987)We’ve known about the planet Venus for a very long time.

Most of the lights in Earth’s sky stay put, relative to each other, and they all spin around the celestial sphere’s poles.

Seven — Venus, Mercury, Mars, Jupiter, Saturn, the moon and the sun — don’t.

Venus never gets very far from the sun, so it’s only seen in the morning or evening sky.

Some folks, like the ancient Greeks, had one name for Venus when it was a morning star and another for the evening star.

Those names go back at least to Hesiod’s day, two and three quarters millennia back.

But before that, around the time construction started on Stonehenge, folks in what we call Mesopotamia had a single name for Venus: Inanna. That was around 3000 B.C., during what archaeology buffs call the Jemdet Nasr period.

We know about the 3000 B.C. Venus observations, thanks to a cylinder seal found near today’s Jalibah, Iraq.

The next Venus-related record I know of is what we call the Venus tablet of Ammisaduqa.

Ammisaduqa was Babylon’s king around the time Egypt’s Thirteenth Dynasty was winding down, when the Late Bronze Age Collapse was still four centuries in the future.

The last I heard, academics still haven’t decided whether Homer’s epics were based on actual events, but for some reason there’s a consensus that the Late Bronze Age Collapse was real.1 And that’s another topic.

Telescopic Views

Frank R. Paul's 'The Man From Venus', Fantastic Adventures back cover. (July 1939) via David S. Zondy's Tales of Future Past [], used w/o permissionNext — skipping lightly over Aristotle, Gan De, Ptolemy, Abd al-Rahman al Sufi and Copernicus — in 1761, Mikhail Lomonosov noticed that Venus has an atmosphere.

I gather that he saw a fuzzy arc during the 1761 transit of Venus, and that academics were debating what he actually saw until at least 2012.

Lomonosov used a telescope. So did Giovanni Domenico Cassini, Johann Hieronymus Schröter and Chester Lyman. Not the same telescope, of course.

Cassini and Schröter figured that a day on Venus lasted about 24 hours, based on markings they saw. Or thought they saw.

Until the mid to late 19th century, when John Draper and others began taking photographs through telescopes, astronomers made observations by patiently looking through their telescopes, sometimes for hours.

The human brain is very good at pattern recognition. So good that sometimes it shows us patterns that aren’t really there. Pareidolia is a five-dollar word for the sort of perception that lets us see the Man in the Moon, happy electrical outlets and Martian canals.

Although I haven’t confirmed it, I’m guessing that Cassini and Schröter observed something akin to Schiaparelli’s canali. All we can see of Venus in visible light is a nearly-featureless crescent or disk, depending on where it is in its orbit.

Starting in the 1920s, we could pick up a few cloud features by observing with ultraviolet-sensitive cameras.2

Pulp Fiction and the Radar Astronomers

Frank R. Paul's 'A City on Venus', Amazing Stories back cover. (January 1941) via David S. Zondy's Tales of Future Past [], used w/o permissionMeanwhile, pulp science fiction magazines were entertaining and inspiring America’s youth with tales that I’d call reality-based. But not realistic.

“…About the only thing that astronomers knew about Venus in the ’30s was that it was smaller than Earth, had a a bit more carbon dioxide in the atmosphere, and a heck of a lot of clouds. In pure run-with-it logic the clouds meant lot of water and the CO2 meant an atmosphere like prehistoric Earth. Conclusion: Carboniferous swamps over the whole planet inhabited by dinosaurs.
Also Munchkin villages….”
(Venus, Tales of Future Past, David S. Zondy)

Getting back to the non-fiction planet, Schiaparelli said he’d seen a few features on Venus. His best estimate was that it rotated once every 224.7 days, same as its orbital period.

Percival Lowell said pretty much the same thing. Then, from November 1902 to March 1903, Vesto Slipher collected spectrograms of Venus, looking for Doppler shift. He’d been working at the Lowell Observatory.

Lowell said that Slipher’s analysis confirmed his and Schiaparelli’s conclusion. Slipher was more cautious. He said he found “no evidence that Venus has a short period of rotation,” and that “so fast a spin as 24 hours could not have escaped detection.”3

Another big step in Venus studies was radar astronomy. It’s like radio astronomy, except that it bounces radio waves off places like the moon and Venus.

In 1944, Zoltán Lajos Bay started testing a radar telescope at the Research Laboratory of the United Incandescent Lamp and Electrical Co. Ltd., (“Tungsram”), Ujpest.

Ujpest is a district in Budapest. But more to the point, World War II was in progress. So it wasn’t until 1946 that they bounced a signal off the moon. By the 1960s, we’d learned that Venus turns on its axis more slowly than it goes around the sun.

Scientists got radar images of Venus in the 1970s, using the Arecibo Observatory’s thousand-foot dish. They found three bright patches: Alpha and Beta Regio in 1964 and Maxwell Montes in 1967.4

Missions to Venus

The first successful interplanetary mission, Mariner 2, flew by Venus in 1962.

The Venera 4 lander stopped transmitting when atmospheric pressure rose to 22 times Earth’s. That was in 1967. Venera 7’s lander made it all the way to the surface in 1970.

Mariner 4 did a flyby of Venus on its way to Mercury, the Venera 9 lander sent back the first pictures from the surface of Venus. In 1978, the Pioneer Venus Orbiter began mapping the Venusian surface.5

SAR, Science and Magellan

NASA SAR Handbook's illustration: 'Strong scattering in HH indicates a predominance of double-bounce scattering (e.g., stemmy vegetation, manmade structures), while strong VV relates to rough surface scattering (e.g., bare ground, water), and spatial variations in dual polarization indicate the distribution of volume scatterers (e.g., vegetation and high-penetration soil types such as sand or other dry porous soils).' (2019)
Cool SAR stuff: using polarized microwaves to ‘see’ what’s on a surface. (NASA)

NASA SAR Handbook's illustration: 'Geometry of observations used to form the synthetic aperture for target P at along-track position x = 0.' (2019)And that, finally, brings me to the Venus Orbiting Imaging Radar mission.

A 1978 study said that Synthetic Aperture Radar, SAR, would give resolution down to 200 meters.

Then budget problems and the Challenger disaster happened. Venus Orbiting Imaging Radar became Magellan, and was carried to low Earth orbit on the Space Shuttle Atlantis in 1989.

When I showed my oldest daughter an illustration of how SAR works, she said “MATH!“, so I’ll skip the “Synthetic Aperture LSA=BetaR0” stuff. Besides, I’m better with words than with numbers.

Basically, radar resolution depends on the ratio of the wavelength used to the length of the radar’s antenna.

For example, to get 10 meter resolution with a wavelength of around 5 centimeters, you’d need a radar antenna about 4,250 meters long. That’s just shy of two and two thirds miles, which isn’t even close to being practical. Not for a spacecraft.

Magellan’s SAR used 12.6 centimeter radar pulses, but — MATH!

The point is that by collecting several signals as a satellite moves — say, from point X1 to point X2 on that diagram — SAR radar gets resolution that’s as good as it would be if it was using one antenna that’s as long as X1-X2.

From September 1990 to October 1994, Magellan gathered data and sent it back to Earth.6 That’s a whole mess of data, and scientists are still sifting through it.

Active(?) Volcano on Venus: Maat Mons

NASA/JPL-Caltech's computer-simulated global map of Venus, showing location of Maat Mons. (March 17, 2023)
One hemisphere of Venus, with Maat Mons area outlined. (NASA/JPL-Caltech)

One big plus of data from orbiters, Magellan included, is that they can show what an area looks like at different times.

They’ve also let scientists know that the amount of sulfur dioxide and methane in the Venusian atmosphere varies considerably. That’s been a metaphorical smoking gun, evidence that volcanoes might be active on Venus.

But there’s considerable distance between “might be” and “is”.

It took three decades for someone to notice Magellan’s ‘before and after’ SAR snapshots of volcanic vents on Maat Mons.

That seems like a long time. But Magellan sent back a lot of data. Plus, Venus is nearly as large as Earth: so I figure it’s small wonder spotting the two images took time.

Maat Mons is the second-highest mountain and highest volcano on Venus.7 It’s also one of the planet’s volcanoes that scientists thought might still be active. And now we have what looks like solid evidence of a recent eruption.

Volcanic activity on Venus spotted in radar images, scientists say
Ari Daniel, NPR (March 17, 2023)

“Researchers scouring decades-old spacecraft data have found clear signs of recent volcanic activity on Venus. The findings, published in the journal Science, reveal not only that the planet’s surface is currently a turbulent place, but offer insights into its geological past and future.

“By any measure, Venus is a hellscape: crushing pressures, a toxic atmosphere, and surface temperatures hot enough to melt lead. It’s like a scene lifted straight from Dante’s Inferno.

“It’s ‘my favorite planet,’ says Robert Herrick, a planetary scientist at the University of Alaska Fairbanks….”

From the Magellan Archives: a Changing Volcanic Vent —

Robert R. Herrick, Scott Hensley; Science's image: 'Fig. 1. Topography and SAR image of the study area on Venus. The colors indicate elevations, which are measured relative to the mean planetary radius from gridded Magellan altimetry. The x and y axes indicate planetary longitude and latitude, respectively. The background grayscale images are from cycle 1 east-looking SAR. The black rectangle indicates the area shown in Fig. 2.' (March 15, 2023)
Figure 1: the study area in Alta Regio, Venus. The black rectangle shows Figure 2’s area. (March 2023)
Robert R. Herrick, Scott Hensley; Science's image: 'Fig. 2. Radar images of a vent that has changed shape. (A) East-looking cycle 1 image and (B) west-looking cycle 2 image of the changed vent and its surroundings. In the cycle 1 image, the vent appears nearly circular and deep with steep walls. In the cycle 2 image, the vent appears larger, irregular in outline, shallower, and nearly filled. The dashed yellow line outlines radar-bright lava flows visible in the cycle 2 image that were not apparent in the cycle 1 image. (C and D) The same images indicating the manually selected match points (purple dots) that were used to generate relative elevations (overlain in color) and to orthorectify the images. The black box in (C) indicates the extent of the unrectified images shown in (A) and (B). All images are shown in a sinusoidal projection with a projection longitude of 165.359°W.' (March 15, 2023)
Figure 2: Close look at Maat Mons, scanned by Magellan: first (A) from the east, then (B) from the west.
Dotted yellow lines in (B) are new, bright lava flows.
Black box in (C) shows extent of images (A) and (B).
(C) and (D) show match points (purple dots) used to get elevations (overlaid in color) (March 2023)

I would have written a shorter letter, but I did not have the time.
Blaise Pascal, Provincial Letters: Letter XVI (4 December 1656)
via Wikiquote, unknown translator

I’m not in Pascal’s class, which is why I skipped over Synthetic Aperture LSA=BetaR0 and talked about wavelengths and distance.

But I’ve got the same issue with time and writing. Ideally, I’d boil down the following “…differences in imaging geometry…posteruptive vent…” excerpt. But I spent more time than I might have on that five-millennia ‘watching Venus’ summary.

So give this excerpt from the “Surface changes…” article in the Science journal, I’ll show a couple more “before and after” images, taken eight months apart in 1991, and move along.

Surface changes observed on a Venusian volcano during the Magellan mission
Robert R. Herrick, Scott Hensley; Science (March 15, 2023)

“Venus has a geologically young surface, but it is unknown whether it has ongoing active volcanism. From 1990 to 1992, the Magellan spacecraft imaged the planet’s surface, using synthetic aperture radar. We examined volcanic areas on Venus that were imaged two or three times by Magellan and identified an ~2.2-square-kilometer volcanic vent that changed shape in the 8-month interval between two radar images. Additional volcanic flows downhill from the vent are visible in the second-epoch images, although we cannot rule out that they were present but invisible in the first epoch because of differences in imaging geometry. We interpret these results as evidence of ongoing volcanic activity on Venus.”

“…An active vent in Atla Regio
Figure 1 shows gridded Magellan altimetry overlain on Magellan cycle 1 SAR images of an area in Atla Regio, Venus, which extends from 9°S, 170°W to 6.25°N, 151°W, covering ~3.2 × 106 km2. This area contains two of the planet’s largest volcanoes, Ozza Mons and Maat Mons, which have previously been hypothesized to be locations of active volcanism). Magellan observed this area with east-looking images in cycle 1 (incidence angle 45°) and west-looking images in cycle 2 (incidence angle 25°). This area has not been imaged by Earth-based radar, nor was it imaged during the earlier Venera 15 and Venera 16 missions to Venus….”

“We identified a volcanic vent at 1.363°N, 165.359°W that changed shape and expanded ([Figure 2]) in the 8-month interval between the Magellan imaging in cycle 1 and 2 (February to October 1991). The vent is located on the north side of a domed shield volcano that is part of the larger Maat Mons volcano. In the east-looking cycle 1 image, the vent appears near-circular (1.5 × 1.8 km, area 2.2 km2) with steep interior slopes. We speculate that it was a drained posteruptive vent. In the west-looking cycle 2 image, the vent has become larger (4.0 km2) and irregular in shape. In cycle 2, the vent wall, identifiable as bright pixels on the vent’s west side (an east-facing slope) and dark pixels on its east side (west-facing slope), is narrow, so the vent interior and exterior are separated by only a few pixels in the 75 m/pixel radar mosaic. We interpret this narrowness as being due to short vent walls, perhaps only tens of meters high, which implies that the vent is nearly filled to its rim in the cycle 2 image. We speculate that a lava lake formed in the vent interior during the 8-month gap between images….”
(Figure 1, 2: emphasis mine)

— And New Lava Flows, Maybe

Nasa/JPL's Magellan radar images of Maat Mons, showing changing landscape in 1991. Maat Mons is a shield volcano on Venus: the planet's second-highest mountain and highest volcano. (February and October 1991)
Maat Mons: possible new lava flows and a volcanic crater’s growth. (February and October 1991)

That pair of NASA/JPL Magellan SAR radar images, from an article in The Conversation, look a bit like part of Herrick and Hensley’s Figure 3, but I haven’t managed to find the NASA/JPL document they’re from.

The scientists figured that, since the February 1991 image was taken from a different angle than the October 1991 one, differences between the two in how the one crater looks might come from something in the image processing.

So they ran simulated SAR data of a virtual crater, seen from east and west, and came up with a crater that looked round, both ways.

Odds are very good that the crater on Maat Mons grew during those eight months, and was bean-shaped in late 1991. If follow-up work confirms what they’ve said, Herrick and Hensley have spotted the first known active volcano on Venus.

On the other hand, we’ve had other ‘firsts’ in the search for Venusian volcanoes.

Hot Spots, Sulfur Dioxide, Venusian Volcanoes and Acronyms

NASA, JPL-Caltech, ESA, Venus Express: VIRTIS, USRA, LPI's image: Idunn Mons, infrared glow observed by ESA's Venus Express shown in red.
Idun Mons: image showing infrared glow (red) detected by VIRTIS, Venus Express. (2020)

The ESA’s Venus Express orbited Venus from 2006 to 2015.

The spacecraft’s main job was studying the Venusian atmosphere. Its Venus Monitoring Camera, VMC, worked in ultraviolet, visible and near-infrared.

And it carried three spectrometers: including the Visible and Infrared Thermal Imaging Spectrometer, VIRTIS and SPectroscopy for Investigation of Characteristics of the Atmosphere of Venus, SPICAV.

In 2010, scientists published a study that connected hot spots with areas on Venus that looked like fresh lava flows.

Two years later, another study tracked a spike in sulfur dioxide in the planet’s upper atmosphere, followed by a slower decline. The decline looked like a similar drop in sulfur dioxide seen by Pioneer when it arrived at Venus.

Hot spots on ground that look like lava flows strongly suggests recent volcanic activity, but I’m guessing someone came up with another possible explanation.

Sulfur dioxide in the upper atmosphere must have come up from below: recently. It breaks down in a matter of days when exposed to sunlight.

Was that poof that volcanoes were erupting? Maybe not.8

“…’A volcanic eruption could act like a piston to blast sulphur dioxide up to these levels, but peculiarities in the circulation of the planet that we don’t yet fully understand could also mix the gas to reproduce the same result,’ adds co-author Dr Jean-Loup Bertaux, Principal Investigator for the instrument on Venus Express [SPICAV] that made the detections….”
Have Venusian volcanoes been caught in the act?“, Venus Express, ESA (March 12, 2021) [emphasis mine]

Maps, Missions, Maat Mons and More

NASA Ames Research Center, U.S Geological Survey, Massachusetts Institute of Technology's map of Venus, from Pioneer data. (March 1981)
NASA-Ames/USGS/MIT Venus map, from Pioneer data. (March 1981)

Two more excessively-wordy excerpts, and I’ll talk about Venusian maps and mountains.

First, what got this month’s study started:

“…Scientists study active volcanoes to understand how a planet’s interior can shape its crust, drive its evolution, and affect its habitability. One of NASA’s new missions to Venus will do just that. Led by the agency’s Jet Propulsion Laboratory in Southern California, VERITAS – short for Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy – will launch within a decade. The orbiter will study Venus from surface to core to understand how a rocky planet about the same size as Earth took a very different path, developing into a world covered in volcanic plains and deformed terrain hidden beneath a thick, hot, toxic atmosphere.

‘NASA’s selection of the VERITAS mission inspired me to look for recent volcanic activity in Magellan data,’ said Robert Herrick, a research professor at the University of Alaska Fairbanks and member of the VERITAS science team, who led the search of the archival data. ‘I didn’t really expect to be successful, but after about 200 hours of manually comparing the images of different Magellan orbits, I saw two images of the same region taken eight months apart exhibiting telltale geological changes caused by an eruption.’…”
NASA’s Magellan Data Reveals Volcanic Activity on Venus “‘ Ian J. O’Neill (JPL), Karen Fox/Alana Johnson (NASA), Rod Boyce (University of Alaska Fairbanks Geophysical Institute); Jet Propulsion Laboratory, Caltech (March 15, 2023) [emphasis mine]

Next, what Herrick and Hensley have shown, and what they figure they haven’t:

“…On the basis of only one changed feature, we cannot determine how common currently active volcanism is on Venus. We draw a distinction between identifying recent volcanism on a planet and demonstrating that it is currently volcanically active. For example, Mars has lava flows with estimated ages of less than a few million years, but no volcanic activity has been identified over multiple decades of continuous observation. Only one changed feature has been identified in our survey of the Magellan data, and none have been found in kilometer-scale radar observations from Earth that covered ~25% of Venus’ surface. The low detection rate indicates that Venus is less volcanically active than Jupiter’s moon Io, for which over 100 active spots have been imaged. We estimate that our search of the Magellan data has examined ~1.5% of Venus’ surface area….”
Surface changes observed on a Venusian volcano during the Magellan mission“; Robert R. Herrick, Scott Hensley; Science (March 15, 2023) [emphasis mine]

Now, about maps of Venus.

I found a good set of high-resolution maps here:

(Acronym time: LPI is the Lunar and Planetary Institute, USRA stands for Universities Space Research Association.)

Those maps were high-resolution, detailed, and included text in sidebars. But they were a tad too high-resolution for this blog. When I scaled the global projection down to something that would fit on this screen, most of the lettering was blurry. At best.

So I got the “Altimetry of Venus” map, designed for low-resolution displays, here:

Then I downloaded the LPI | Resources “Altimetric and Shaded Relief Map of Venus” and clipped out the east end of Aphrodite Terra and marked Maat Mons’ location. It’s under “Greater Admiration”, the next heading.

Again, Maat Mons is the mountain Herrick and Hensley studied.

Now, about those names. Briefly, for me.

A terra is a landmass, or would be if Venus had an ocean. More than one terra are terrae.

A mons is a mountain, more than one are montes.

Montes and terrae are words from Latin, which we use because today’s naming conventions got started when Latin was a common language for European scholars.

One more thing: Maat Mons is at 0.5°N 194.6°E.9

“Greater Admiration”

Detail, USGS Altimetric and Shaded Map of Venus from Lunar and Planetary Institute, Universities Space Research Association Venus Map Catalog. (1981) location of Maat Mons marked with a red +. Used w/o permission.
Detail, USGS Altimetric and Shaded Map of Venus. (1981) Maat Mons marked with red “+”.

I had, and still have, more to say about Venus.

But I’ve run out of time this week, so that’ll wait.

NASA/ESA's image: Galaxy UGC 9391, which contains two types of stars astronomers use to calculate distances: Cepheid variables and a Type Ia supernova, 2003du. (2016) via BBC News, used w/o permission.I’ll wrap this up by repeating something I haven’t said in a while.

We live in a universe that’s packed with wonders, beauty and harmony.

These wonders and beauty include, I think, places like Venus: which aren’t obviously beautiful in the picture-postcard sense.

Maybe it’s the nerd in me, but I see a sort of beauty in the way physical laws produce so many different — yet similar — landscapes and weather on other worlds.

That strikes me as a reason for “greater admiration” of God’s work. And since I see reflections of God’s beauty — and might — in this world, learning more about God’s creation inspires greater respect for God. It also reminds me that God’s God and I’m not. (Catechism of the Catholic Church, 268ff, 283, 341)

More-or-less related posts:

1 History and a little science:

Giuseppe Arcimboldo's 'Porträtt, karikatyr:' portrait of Wolfgang Lazius. (1562) Photo by Samuel Uhrdin, via Wikimedia Commons, used w/o permission.2 Ptolemy, pareidolia and pulp fiction:

3 Scanning Venus:

4 Mapping Venus:

5 Missions to Venus:

6 More-or-less about Magellan:

7 Maat Mons and Magellan images:

8 Venusian volcanoes, indirect evidence and recent developments:

9 Naming conventions and Venusian features:

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About Brian H. Gill

I was born in 1951. I'm a husband, father and grandfather. One of the kids graduated from college in December, 2008, and is helping her husband run businesses and raise my granddaughter; another is a cartoonist and artist; #3 daughter is a writer; my son is developing a digital game with #3 and #1 daughters. I'm also a writer and artist.
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