Slashdot Mirror
Atomic Oxygen Detected In Martian Atmosphere (cnn.com)
An anonymous reader quotes a report from CNN: Atomic oxygen has been detected in the atmosphere of Mars, according to NASA. The atoms were discovered in the Martian mesosphere, the upper layers of the red planet's atmosphere. This discovery will enable researchers to have a better understanding of the elusive Martian atmosphere. Atomic oxygen can help scientists determine atmospheric erosion and how other gases escape Mars. It also affects the radiative cooling from the carbon-dioxide bands in the Martian thermosphere, which is above the mesosphere. The atomic oxygen discovery was made using an instrument on board the Stratospheric Observatory for Infrared Astronomy, or SOFIA. SOFIA is a Boeing 747SP jet that has been modified for research purposes to carry a 100-inch diameter telescope. Using the German Receiver for Astronomy at Terahertz Frequencies, known as GREAT, allowed researchers to distinguish between oxygen from our atmosphere and that of the Martian atmosphere. They discovered half the amount of atomic oxygen expected, most likely due to variations in the atmosphere itself, and scientists will continue to use SOFIA to study the Martian atmosphere.
Venus is far better than Mars. Specifically, Venus's cloudtops - say, 54km altitude, 70 latitude (poleward might be even better, but you start facing more risk from the polar vortices, so we'll just compare 70). Earth by comparison will be equatorial, and Mars will be surface-average.
Gravity (earth relative): Earth: 1.0; Mars: 0.38; Venus: 0.9
Air pressure (atm): Earth: 1.0; Mars: 0.006; Venus: 0.5
Temperature (avg, C): Earth: 26; Mars: -30; Venus: 31
Daily variation (C): Earth: 4-30; Mars: 90; Venus: 15
Day length: Earth: 24; Mars: 24.5; Venus: 48
Ability to relocate / explore new terrain: Earth: moderate; Mars: poor; Venus: high
Overhead radiation shielding mass (meters H2O equivalent): Earth: 10,3; Mars: 0.36; Venus: 5.2
Magnetic field: Earth: 25-65uT, intrinsic; Mars: induced, 20-40nT MPR, 5-20nt magnetosheath; Venus: induced, 40-80 nT MPR, 10-40nT magnetosheath
Health hazards: Earth: those humans evolved to; Mars: 1) Fine, abrasive electrostatic dust, 2) silicosis; 3) perchlorates; 4) hexavalent chromium; 5) other chemical hazards; Venus: 1) Corrosive acid mists; 2) hydrogen fluoride; 3) probably others of relevance
Other local hazards: Earth: those humans evolved to; Mars: marsquakes, landslides, dust storms, probably others. Venus: poorly understood - lightning (although we don't know at what altitude), gusts/shear (probably Earthlike, but poorly quantified), icing (probably not, but maybe), possibly others. Needs more study, but Mars gets the lion's share of the planetary exploration budget and everything else competes for the scraps.
Delta-V to habitable area from LEO (km/s, aerocapture assumed): Earth: 0; Mars: 4.7; Venus: 4.2
Delta-V from habitable area to LEO (km/s, aerocapture assumed): Earth: 9.8; Mars: 10.0; Venus: 15.5
Transit time (months): Earth: 0; Mars: 9; Venus: 5
Launch window frequency (months): Earth: 0; Mars: 25; Venus: 19
Landing difficulty: Earth: moderate (dense atmosphere, oceans to land in, compacting soil, readily available rescue); Mars: hard (reversed conditions of Earth): Venus: easy (no landing at all; your landing ellipse is "a large chunk of the planet")
Solar energy (29% triple-junction W/m): Earth: 290; Mars: 45; sometimes almost none; Venus: 400
Capturable wind energy: Earth: moderate; Mars: effectively none; Venus: high
Diversity / value of resources: Earth: moderate (that which we're used to); Mars: probably less than Earth, but not "poor"; Venus: the planet acts as a natural refinery, baking / dissolving minerals from rocks and redepositing them in other forms; surface appears to be highly enriched in "incompatible elements" (many of which are rare and valuable on Earth) and the planet is highly enriched in deuterium.
Accessibility of resources: Earth: moderate (that which we're used to); Mars: like Earth, but hindered by mobility and the difficulty of removing overburden; Venus: mixed high/low; a large resource base is available to be drawn directly from the atmosphere and which can be distilled /decomposed by simple heating/cooling (for example, 85% H2SO4 -> H2O + O2 + SO2) - the list of known/likely elements in the clouds is very long, even involving significant iron in the form of iron chlorides). However, surface access requires heat-tolerant phase change balloons (the high atmospheric density makes "dredging" with the same fan used for maneuvering a reasonable approach)
Venus is grossly underappreciated as a destination for human settlement, and for exploration in general. Normal Earth air is its own lifting gas. Rather than living in a cramped pressure vessel, colonists would be living in an expansive, bright space perfect for cultivation. Don't like one of your coworkers? Go hang your "room" from a catenary cable on the opposite side of the habita
Monkeywrench Ex Machina.
Also note that if you were to concentrate Martian air to 1ATM and simply add oxygen to reach an Earthlike O2 partial pressure, it would be highly toxic. 1% CO2 causes drowsiness, while 7-10% is lethal. Also, Mars's atmosphere is 0.0557% carbon monoxide, which while not acutely lethal is well above the toxicity limit where acute symptoms and irreversible, accumulative neurological damage occurs.
Monkeywrench Ex Machina.
Martian and lunar dust have both similarities and differences. Martian dust particles are finer, athough it doesn't make them less hazardous. Despite attempts to minimize it, some exposure to the dusts will be inevitable; it's fine, ubiquitous and sticks to everything. It's well recognized as a significant hazard in mission design. One hazard of martian dust over lunar dust is that it appears to contain significant more chromium, and it's often hexavalent (a highly toxic form rarely found in nature on Earth). A number of other compounds such as arsenic appear to be of relevant risk as well.
Expecting to survive a crash landing on Mars is far beyond positive thinking.
The landing processes on both planets start out roughly the same. But the processes on Venus end before the hardest parts of a Martian landing end. Once you're down to under 100m/s or so on Venus, you're ready to start with deployment**. Once you're down to ~100m/s on Mars, you still have the part that's most likely to kill you remaining.
** - Although any type of reentry system works, a ballute reentry seems particularly well-suited for Venus, as it give you an initial inflation of warm, light gases. Ballute reentry has been proposed on a number of Venus proposed Venus probes, but so few Venus probes ever get funded due to Mars' domination in the budgeting process.
Not probably - it does. But it's not in the atmosphere. It's frozen in permafrost, mixed with sand and gravel and contaminated with a good number of toxic substances. And Martian backhoes aren't exactly dime-a-dozen / low-maintenance objects.
Venus's water for a colony comes from the mists. There are two potential sources: 1) direct absorption, and 2) condensation.
1) The habitat requires propulsion no matter what. This is because in addition to the strong zonal winds that comprise the superrotation, there are weaker meridional winds that would cause a craft to drift from its desired location. While the zonal winds are too strong to overcome (nor would you want to), the meridional winds are nothing particularly challenging for an airship. An aircraft under propulsive load will have a constant stream of air moving past it - fastest directly in the propeller wash. Hence, the best way to get lots of mist along lots of surface area is to handle steering with a flexible windsock-style thrust vectoring system comprised of permeable tubing for direct absorption, and/or hydrophilic collection/drainage surfaces (see #2). Hence, the collection system is little added mass over the base propulsion system. In the case of absorption, the absorption fluid would be weak H2SO4.
The ideal situation involves large volumes of air moving at (relatively) low speeds. This means a large propeller. Hence, the ideal design for launch on a mid-sized rocket involves a propeller with two 6m folding blades stowed vertically in the center of the packed habitat during launch and cruise, rather than multiple smaller propellers stacked horizontally. A large prop is also more efficient.
2) Direct collection on the envelope. While the original Vega data was interpreted as there being no condensation/rain on the balloons, some more recent work has challenged that view, suggesting that it indicates progressively increasing mass loadings as moisture collects, then peaking as runoff rates matched collection rates. This is intere
Monkeywrench Ex Machina.
Let's compare individual resources, shall we?
Water:
Mars: frozen in permafrost, mixed in with sand and gravel, containing perchlorates, hexavalent chromium, and other toxic chemicals. Have to build and deploy a Martian equivalent of a bobcat and scrape it out (note that mining equipment is famous for high maintenance needs). If chunks are too big they need to be run through a rock crusher. They then need to be loaded into a bin and pressure sealed, then heated, with the steam driven off creating the necessary pressure for water to be able to exist at a liquid state and flow off through filters (which will need periodic cleaning); the sand and gravel has to be emptied. The contaminated saltwater now has to either be distilled or run through reverse osmosis, the latter being unfortunately rather contaminant sensitive. It's enough of a headache that most near-future proposals just call for bringing the water (or just hydrogen to make it) from Earth.
Venus: Acidists naturally condense or absorbed (see an above post on the subject) and run straight into a boiler. There they're heated. Free water is driven off and H2SO4 decomposes, emitting more water. The steam is isolated and condensed.
The latter is much easier.
Oxygen.
Mars: There are two main proposals for oxygen production. One is electrolysis. Electrolysis systems as used on ISS have however proven to be rather finnicky, and you're dependent on the water mining above to replace any water loss in the system (which will happen over time). The other proposal is to be tested on Mars 2020: MOXIE. Martian air is drawn in and compressed, troublesome impurities removed, CO2 frozen out then reboiled at pressure, then run through a SOFC which uses a lot of electricity to turn CO2 into O2 and CO.
Venus: SO3 decomposes at elevated temperatures (much faster in the presence of a catalyst) into O2 and SO2. So the only added step here over water production is the catalyst. Separation from SO2, O2, and other elsser chemicals can be done in a specialized stage or in distillation.
Again, winner: Venus.
Let's look at starting to form an industry. So, let's look at the top 10 industrial chemicals on Earth
H2SO4: This is the number one produced chemical on Earth. Do we even need to go into how much easier it would be to get on Venus?
N2: Venus's atmosphere is denser than Mars's and N2 is about in the same percentage concentration, so the advantage is again to Venus.
C2H4: The process is roughly the same on both Venus and Mars
O2: Already covered.
Chlorine (Cl2): On Venus, this is conducted by the Deacon process (4 HCl + O2 = 2 H2O + 2 Cl2). You get free HCl from distillation and you have cheap O2. On Mars, this would be done by the much more energy-intensive electrolysis of brine. Furthermore, you'd need to either isolate out brines containing specifically chlorides first.
Ethylene Dichloride (C2H2Cl2): Used for PVC, which honestly isn't a great material for either Mars or Venus. The routes are basically the same on both Mars and Venus.
Phosphoric Acid (H3PO4): On Venus, this comes for free during distillation. On Mars... honestly, we don't really know. We've found phosphate minerals (chlorapatite and merrillite) but no concentrations of them.
Ammonia (NH3): Haber process, same on both planets.
Sodium Hydroxide (NaOH): Ah, finally something Mars can win at! Various hydroxides will be produced as a byproduct of chlorine production. As far as is known, both sodium (and similar-use potassium) can't be gotten from the atmosphere (although they're abundant in any surface rocks that may be mined for other purposes - Venus's surface-mining throughput potential being lower than that of Mars'). That said, Venus lends itself perfectly to cation recycling. Any waste (plant, human, industrial
Monkeywrench Ex Machina.
I have trouble reconciling your post with you having read mine. You wrote:
My post has nothing to do with colonizing Venus's surface. Nothing to do with the high temperatures there. Nothing to do with the high pressures there. To a Venus colony, the surface is only secondary - for exploration and low-throughput collection of valuable / low quantity minerals. Both the living area and the main source of raw materials is the atmosphere itself.
An early to mid-stage Venus colony doesn't even need a surface probe.
Also, what you wrote is hyperbole. There are plenty of materials that tolerate Venus's environment well. Two popular ones these days are PTFE and vectran. VEGA used PTFE, although modern variants involving copolymerization with for example PPVE (Teflon NXT) or HFP (Teflon FEP) perform better in a lot of key aspects. VEGA also wasn't reinforced with a high tensile ripstop; the PTFE itself was loadbearing and the balloon superpressure, which is obviously not a scalable solution (it was more like a party balloon than a blimp ;) ).
That is precisely what I was writing about, colonizing Venus before terraforming it.
If your issue is with people's mistaken perceptions about Venus what a colony on Venus would be like, that's indeed something I seek to change. People tend to think of Venus as its surface. But the habitable area is the middle cloud layer.
Monkeywrench Ex Machina.