The geological history of Venus: What’s known, not known, and unknown.
The geological history of Venus: What’s known, not known, and unknown.
This is a very clearly written overview by James Head, one of the world’s preeminent planetary geologists, of what has been learned about the geology of Earth’s sister planet, the planet of a million volcanoes. Key quote:
Many features on Venus (folded mountain belts, rift zones, tesserae) were like Earth, but there were few signs of Earth-like plate tectonics, so that Venus seemed to have a single lithospheric plate that was losing heat conductively and advectively. But the cratering record presented a conundrum. First, the average age of the surface was <20% of the total age of the planet, and second, the average was not a combination of very old and very young surfaces, such as Earth’s continents and ocean basins. Third, the lack of variability in crater density, and of a spectrum of crater degradation, meant that all geological units might be about the same age. This implied that the observed surface of Venus must have been produced in the past hundreds of millions of years, possibly catastrophically, with very little volcanic or tectonic resurfacing since then! Suddenly, Venus was not like Earth, nor like the Moon, Mars, or Mercury.
Some scientists even believe that Venus was essentially resurfaced in a massive volcanic event about a half billion years ago. Others disagree. Meanwhile, the European probe Venus Express has gotten hints that volcanic activity is still going on.
As Head concludes, it has been 20 years since the last spacecraft arrived at Venus to do geological research. It is time to return.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
The geological history of Venus: What’s known, not known, and unknown.
This is a very clearly written overview by James Head, one of the world’s preeminent planetary geologists, of what has been learned about the geology of Earth’s sister planet, the planet of a million volcanoes. Key quote:
Many features on Venus (folded mountain belts, rift zones, tesserae) were like Earth, but there were few signs of Earth-like plate tectonics, so that Venus seemed to have a single lithospheric plate that was losing heat conductively and advectively. But the cratering record presented a conundrum. First, the average age of the surface was <20% of the total age of the planet, and second, the average was not a combination of very old and very young surfaces, such as Earth’s continents and ocean basins. Third, the lack of variability in crater density, and of a spectrum of crater degradation, meant that all geological units might be about the same age. This implied that the observed surface of Venus must have been produced in the past hundreds of millions of years, possibly catastrophically, with very little volcanic or tectonic resurfacing since then! Suddenly, Venus was not like Earth, nor like the Moon, Mars, or Mercury.
Some scientists even believe that Venus was essentially resurfaced in a massive volcanic event about a half billion years ago. Others disagree. Meanwhile, the European probe Venus Express has gotten hints that volcanic activity is still going on.
As Head concludes, it has been 20 years since the last spacecraft arrived at Venus to do geological research. It is time to return.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
So not much as changed since Magellan. Which I guess isn’t surprising. Nova did a great special in the 90’s about Magellan’s work this makes it sound like its still mostly current.
Sadly considering the track record for probes making it to the surface of Venus its unlikely anyone is going to front the money anytime soon for something to get crushed or get 20 minutes of data for a billion bucks.
Just to set the record straight, the last five Soviet Venus landers, Venera 10 through 14, all operated for more than hour on the surface, with the average generally closer to two hours. Venera 13 for example operated for more than 2 hours.The two probes before that all operated for more than 50 minutes, while Venera 7, the first to successfully send back data, operated for 23 minutes. See The Chronological Encyclopedia of Discoveries in Space, pages 92, 106, 136, 161, 162, 182, 183.
Granted, the cost was high for so little operating time, but considering the hostile Venus surface environment these missions were hardly failures, they were engineering achievements of the first order.
Why go to the surface? It might be more worthwhile to have some bots higher up in the atmosphere.
You learn a lot by working the atmosphere. In fact, it’s already been done by two French balloons that floated in the atmosphere for two days back in 1985. Nonetheless, to study the geology you have to go down to the ground and sample it, like the rovers on Mars are doing.
‘I would give Venus a very low priority for funding. It’s a very nasty place. A Martian probe may last for years, and we may send people there someday. Not so our sister planet, unfortunately.
It may not be a place that we will go to, but as we explore the universe and look for other habitable planets, it is always good to know what kinds of planets there are, how they formed, and whether we could one day teraform them. It may be too early to prosper from all the answers that we can get from Venus, so the return on investment is lower than other explorations, but the answers are good to know, as they help us fill in pieces of the puzzle that is the universe.
Some day we may figure out how to build a rover for Venus that will last a decade.