Future Venus Missions |
Future Venus Missions |
Jul 1 2005, 01:30 AM
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#201
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Solar System Cartographer Group: Members Posts: 10185 Joined: 5-April 05 From: Canada Member No.: 227 |
Oh well, might as well start that new topic since it's already well advanced in the Juno area...
My perspective on landers is as follows. All the landers we've had so far were dropped blind onto an essentially unknown surface. Any future landers can be targeted for specific terrains. It really is not true that we have had representative landings. Even a descent image or two, a panoramic photo plus a bit of surface composition, from a simple Venera-class lander just updated a bit, would be useful if we could put several down at well chosen targets. My choices would be: Examples of the main plains units (smooth, fractured, ridged) tesserae high elevation radar-bright tesserae large fresh lava flow unit ('fluctus') crater dark parabola crater ejecta outflow unit dunes area. And I have always assumed, rightly or wrongly, that it would be relatively easy to put these down, so they ought to be fairly inexpensive as planetary landers go. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jun 3 2021, 08:03 AM
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#202
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Member Group: Members Posts: 315 Joined: 1-October 06 Member No.: 1206 |
That's excellent. Lets hope against hope for at least 30 minutes then.
Maybe a shot or two from the surface a la Huygens? P |
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Jun 3 2021, 08:37 AM
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#203
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Reading up on the science of noble gas abundance in planetary reservoirs, I gained a newfound appreciation of why we need vastly better measurements than had previously been made at Venus.
While there is often an interesting story to be interpreted regarding the ratio of the top two or three isotopes, the full picture is much more complex, and to take the most challenging case, xenon has nine isotopes that are (basically) stable [seven truly stable, and two have extremely long half-lives]. In Earth's atmosphere, xenon abundance is 87 parts per billion, so the individual isotopes are, obviously, in some cases more than 9x less abundant than that. To measure their abundance with even one significant digit means measuring atmospheric components to better than 1 part per billion, and ideally even several times more accurate than that. To date, 1970s-era instruments have returned the best data, and those placed only loose constraints on the abundance of xenon in Venus's atmosphere. Basically, good data for krypton and xenon don't exist at all. Now, if this seems arcane, here's the stunner – we are still searching for an explanation for the unexpectedly low xenon abundance in Earth's atmosphere! (When we don't understand something about Earth, that's a strong sign that we don't understand it for planets in general.) In matters of noble gas abundance, Earth is just one case, with Mars, the solar wind, Jupiter, and meteorites being other cases. And so, Venus is potentially a very important case for understanding not merely the evolution of the atmosphere of Venus, but even of Earth… and, we can be sure, for understanding terrestrial exoplanets outside our solar system. For what it's worth, Titan is apparently another beast altogether, due to the physical chemistry of ices and noble gases although ice has been at least discussed as a possible reservoir for Earth's "missing" xenon. So, the atmospheric composition instruments on DAVINCI+ may lead to realizations of extremely broad reach, even so far as the history of Earth is concerned. |
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