Featured at LPSC 2017
I returned a couple of weeks ago from the Lunar and Planetary Science Conference (LPSC) 2017 in Houston. This is one of the major international events where planetologists, astronomers, representatives of space agencies and universities from around the world talk about new research and plans for the future.
After reading a couple of hundred reports and poster presentations, here I want to share a summary of the works that seemed interesting.
Disclaimer I am a physicist by training, but still not a specialist in planetology. My selection of material is probably subjective and incomplete. My interpretation of the work may be erroneous. If for you such things as finances, work, or professional reputation depend on its accuracy, then it is better to contact the authors and double-check everything with them directly. Their contacts are indicated in the abstracts of the works under the links. Corrections from readers are, of course, welcome.
So let's go!
TRANSIENT BROAD SPECULAR REFLECTIONS FROM TITAN'S NORTH POLE The
glint of the Sun in the lakes of Titan has been photographed for quite some time:
[Sunlight on Titan. Image Credit: NASA]
However, recently, such reflections have begun to be noticed where no lakes exist. Moreover, they are inconsistent. Today it sparkles, in the next flight with a very similar geometry - no longer. What's the matter?
To explain the hypothesis of "wet asphalt." Imagine that a methane rain passed over a slightly rough terrain. Asphalt gets wet and glitters. By the next passage of the Cassini over the terrain, it has dried up and reflections are no longer observed:
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METHANE, ETHANE AND NITROGEN LIQUID STABILITY ON TITAN Let's
continue about the hydrosphere of Titan. Developed, with seas and rivers. True, the prefix "hydro" is not entirely appropriate here, because there is no water in those seas, but they are filled with liquid methane (CH 4 ), ethane (C 2 H 6) and nitrogen (N 2 ). It is not very clear only in what proportions and how these substances generally interact under the conditions of Titanium. What is the work about? It’s quite a laboratory.
The authors took these three gases, cooled them to cryogenic temperatures, and began to watch how they mix and when they freeze, depending on concentrations and pressures. And they discovered things in the light of which the hydrosphere of Titan looks like a much more complex system compared to the oceans on Earth. However, if instead of one you have three “waters” and three different ice, then something like this was to be expected.
The methane-ethane mixture freezes in more severe frost than each of the gases individually. That is, these gases work as mutual antifreezes.
When this mixture freezes, methane ice floats to the surface, while ethane ice sinks and falls to the bottom. Which is formed first - depends on the initial concentration.
[Photo of an experimental camera from work. On the left is ethane ice at the bottom of the liquid mixture. On the right is methane on its surface. Image Credit: J. Hanley, L. Pearce, G. Thompson, W. Grundy, H. Roe, G. Lindberg, S. Dustrud, D. Trilling, S. Tegler / Lowell Observatory, Flagstaff, AZ; Northern Arizona University, Flagstaff, AZ; University of Texas, Austin, TX.]
Further, the ingress of nitrogen into the mixture (simply from the atmosphere) can increase the melting point of the mixture and, accordingly, lead to its unexpected freezing. By the way, in another worknitrogen has been shown to dissolve well in methane - but poorly in ethane. Thus, the evaporation of a part of methane from a liquid can cause a sudden “boiling” of the sea. A kind of cryogenic champagne with nitrogen bubbles.
Finally, the most interesting. At pressures of more than 2.5 atmospheres (corresponding to depths of more than ~ 100 meters on Titan), the methane-ethano-nitrogen mixture is divided into two liquid phases. The report was an amazing video, here you have to limit yourself to a not-so-good picture:
[Image Credit: J. Hanley, L. Pearce, G.Thompson, W. Grundy, H. Roe, G. Lindberg, S. Dustrud, D. Trilling S. Tegler / Lowell Observatory, Flagstaff, AZ; Northern Arizona University, Flagstaff, AZ; University of Texas, Austin, TX.]
Above is gas. Below it is the first liquid phase rich in ethane. Under it is a second, rich in nitrogen. And on the “ceiling” of the first phase, a tiny hint of a droplet is visible. This is a condensate of the second phase. Which with real drops, like oil in water, flows through the light of the first into the second.
Have you imagined two-layer seas? So do I.
After the report, I thought about something else. The terrestrial oil industry has long been engaged in the cryogenic separation of associated gases. Of which the very first are methane and ethane. Well, nitrogen and the atmosphere is full. So, perhaps, with all these interesting effects in oil refining people are already familiar. It is difficult not to pay attention to the suddenly frozen (from the ingress of nitrogen) pipeline. But if this is so, then surely all these studies are deeply closed corporate secrets ...
--- === ---
CLASSIFICATION OF LABYRINTH TERRAINS ON TITAN The
labyrinths of Titan are plateaus cut by a complex system of valleys and ridges that visually resemble the bark of a tree:
[Image Credit: NASA / JPL]
Their nature is not quite clear. At first glance, they look like river beds - and we know that there are rivers on Titan. But, looking more closely, you can see that some of these "labyrinths" are closed. They do not "flow" from nowhere.
So, at least part of the labyrinths is not a channel? The authors took up morphological analysis and concluded that some of these formations are supposedly ... karsts ! But what exactly gives rise to them — whether dissolution of material by underground flows, flushing or evaporation — remains unknown.
Are not the labyrinth plains on Titan made of similar scourges?
--- === ---
TOPOGRAPHIC ASSESSMENT OF HOLLOWS ON MERCURY: DISTINGUISHING AMONG FORMATION HYPOTHESES
Since we are talking about karsts , it makes sense to transfer to Mercury. Mysterious pits ("hollows") on it have not yet been properly explained. But one hypothesis claims that it ... is also karst. Formed by the evaporation of some volatile substance under a layer of dust and regolith.
This is what they look like:
[Pits on Mercury. Yes, one should try to see holes in these spots, not ledges, and concave craters in rounded tubercles. Sometimes a rotated picture helps, so I added one. Image Credit: NASA]
We do not know what this material is. And I don’t even know if the hypothesis is true. In this work, I just liked the pictures. Good, beautiful photographs of the "pits" collected by the authors in order to classify them and presented to the public. The numbers I wrote down. And the authors forgive me, I laid out one, slightly taking photos to raise the contrast. In my defense, I note that the pictures on the presentation also looked much better than the originals from the MESSENGER website.
[Image Credit: NASA / JPL]
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OXYGEN DEPLETION ON THE SURFACE OF MERCURY: EVIDENCE OF SILICON SMELTING?
After spending 4 years in orbit around Mercury, the MESSENGER device was able to measure the content of the main mineral-forming elements (O, Si, Ti, Al, Cr, Fe, Mn, Mg, Ca, Na, K, S, Cl) in the surface of the planet.
True, the device only sees the concentration of atoms, and not the chemical bonds between them. To evaluate the mineral composition, all metallic elements are usually assumed to be completely oxidized. That is, silicon, for example, is present as SiO 2 , aluminum as Al 2 O 3, and the like. Of the obtained oxides, then, as from the constructor, minerals are composed (for example, calcium silicate Ca 2 SiO 4 is 2 * CaO + SiO 2 ).
Everything would be fine, but only for Mercury it does not work. The oxygen balance does not converge. It turns out to be insufficient to oxidize everything that is oxidized, while maintaining the measured ratio of oxygen to silicon O / Si = 1.4 ± 0.03 (and even less, as stated in the work).
In an attempt to explain this discrepancy, a hypothesis was put forward: a kind of “metallurgical smelting” of pure silicon from quartz and graphite takes place in the depths of Mercury, which, as we strongly suspect, accounts for several percent of the planet’s crust.
If this is true, then 12.6–17.9% (by weight) of the surface of the northern hemisphere of Mercury should be formed by metallic silicon or its alloy with iron.
Why is this interesting? Well, firstly, unoxidized silicon as a rock-forming substance is unusual. Secondly, on all other rocky bodies (Moon, Earth, Mars) there is an excess of oxygen and everything that, in principle, can be oxidized by it, has been oxidized for a long time. Why is this suddenly not the case on well-sun-fried Mercury? The riddle.
[Mercury and silicon. Left Image Credit: NASA / JPL; Right Image Credit: Wikipedia]
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LUNAR CRUSTAL MAGNETIZATION INFERRED FROM CHARACTERISTICS OF LUNAR SWIRLS
I thought that I knew a lot about the Moon. But, as it turned out, he was not aware of the existence of “ lunar diffuse structures ” ( lunar swirls ). Moreover, I can’t even imagine what the official name of this phenomenon is in Russian. On the Internet there are “vortices”, “turbulences”, “curls”, “albedo anomalies” and “diffuse structures”. The latter, although less often, but in more serious sources, so I will use this term.
Opened back in the 1960s, these structures still represent a mystery. Outwardly, they look like light stripes and spots, with a kind of periodic pattern:
[Lunar diffuse structures. Left Image Credit: Wikipedia; Right Image Credit: NASA]
This pattern vividly reminded me of the pictures that appear on an electron beam TV when a magnet is presented, if anyone remembers this phenomenon. This similarity is reflected in one of the hypotheses explaining diffusion structures. It is believed that under them in the lunar soil lie natural permanent magnets. Say, a magnetized lava tube or the remains of an iron meteorite. With their magnetic field, they deflect energetic charged particles of the solar wind, not allowing them to bombard the surface - and therefore it remains light. A kind of invisible protective dome over the terrain. By the way, these structures are indeed associated with magnetic anomalies.
The work itself is about evaluating the parameters of a buried magnet, but I already had enough surprise.
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HOW DIELECTRIC BREAKDOWN MAY WEATHER THE LUNAR REGOLITH
Not only meteorites plow the lunar surface. It turns out that the solar wind, especially on a moonlit night, makes a quite comparable contribution. How? A stream of energetic electrons. Which can fly to the night side of the Moon and charge there regolith particles to tensions of ~ 10 6 V / m. Which leads to explosive electrical breakdown. The material in the breakdown channel evaporates, adding gas to the rarefied lunar atmosphere, and the dust particle is destroyed or re-melted. Soil, as a result, is slowly mixed up. This works the better, the darker and colder the terrain (in heat, the charge "flows" with normal conductivity).
So, who knows, maybe the traces of the astronauts will not be erased not by dust from a meteorite falling nearby, but by gradual evaporation from trillions of microscopic electrical breakdowns?
[Also electric discharge, but larger]
--- === ---
SPACECRAFT IMPACTS ON THE MOON: CHANG'E 1, APOLLO LM ASCENT STAGES
Electronic poster
Cosmonautics already has its own archeology. Looking at modern orbital images of planets, people find there devices that reached these celestial bodies decades earlier (see, for example, the magnificent story about Mars-3 ).
The author of this work specializes in traces of the fall of the lunar apparatus, collecting a whole collection of them. This year, four more were added to them: from the take-off steps of Apollo 12 and -14, the Chinese Chang'E 1, and, more recently, from the European SMART-1.
[Traces of the fall of the takeoff stage of Apollo 12. Image Credit: NASA / Philip J. Stooke] It was
slightly surprised (besides the topic itself) that many falls left behind not craters at all, but strokes and stripes. Apparently, speeds of 1 km / s and below are not enough for explosive destruction of the apparatus or soil, and sliding contact simply leads to the scattering of debris over a long distance along the direction of the orbit.
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SIZE AND SOLAR INCIDENCE DISTRIBUTION OF SHADOWS ON THE MOON
It is hard to believe that the Moon, already examined for more than half a century along and across, in 30-centimeter resolution "photographed from the face and back", covered with 180 tons of human debris , may still hold something else mysterious. Yes, and in such a banal, it would seem, things like shadows.
And yet.
The authors took up a simple and seemingly boring activity. They began to study the size distribution of moon shadows. Statistics in its purest form. But not obvious. After all, a shadow is a complicated thing. With a "gliding" morning incidence of rays, the characteristics of the terrain depend extremely non-trivially.
And dug up. The density of shadows with sizes of 3-100 meters, firstly, does not depend on their size, and secondly, does not have a clear explanation. So, there is something like this in the distribution of the bumps of the lunar surface on these scales, which we do not yet understand. People at the conference asked smart questions, compared something with the distribution of crater sizes, were surprised, but I won’t take it now.
It would seem that the golem statistics of black and white spots, but brought to mind - and it turns out that another mystery lies on the long-studied moon. Somewhere in a deep shadow ...
[Picture from work. Image Credit: Oded Aharonson, Paul O. Hayne, Norbert Schorghofer]
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PENITENTES AT TARTARUS DORSA, PLUTO
Calgaspores (they are also penitentes, penitentes) - beautiful and unusual fields of snow-ice needles:
[Kalgaspory. Image Credit: Wikipedia]
[Calgaspore. Image Credit: Wikipedia]
Until now, they were known only on Earth. But, according to the latest data, it seems that they are also found on Pluto.
Of course, no one saw them there. But the authors of the work argue that these long stripes in the photograph “are well described by theoretical models of calgospores, and their interval, orientation, and growth rates are in good agreement with observations of New Horizons methane ice on Pluto.”
[Pluto, region of Tartarus Dorsa. Image Credit: NASA / JHUAPL / SWRI]
And yes, most likely the Pluto calgaspores consist of methane (CH 4 ) ice.
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BISMUTH TELLURIDES AND SULFIDE MIXTURES AND THEIR RELATION TO METAL FROST ON VENUS
Something quite reminiscent of snow can be seen on the radar images of the Venusian hills. But, of course, at 500 degrees Celsius this should be something else. Something with high reflectivity and high dielectric constant. Perhaps almost metallic in nature. What exactly?
["Snow" in the Maxwell Mountains on Venus. Image Credit: NASA / Magellan]
The authors suggested that these are tellurides or mixed bismuth sulfides ( Bi 2 Te 3 , Bi 2 Te 2 S) Having recreated Venusian under laboratory conditions, they watch how these substances are sublimated and interact with the atmosphere. Trying, in particular, to understand whether they, like earthly snow, will settle in the Venusian mountains in the 300-degree "frost" there.
The conclusions are mixed, and in general the work did not seem to me particularly convincing. Assumptions and alternative explanations are visible even to a layman. But the imagination of this "semiconductor snow" spurs, and therefore leave it on the list.
[Bismuth sulfide telluride, it is tetradimite. Image Credit: Wikipedia]
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THE BIOPAUSE PROJECT: BALLOON EXPERIMENTS FOR SAMPLING STRATOSPHERIC BIOAEROSOL
Those who read the Kraitonovsky Strain of Andromeda will immediately appreciate the charm of this research. The idea is the same: to get closer to outer space, “scoop up” life from there and bring down for study. In order to understand how far earthly life extends into the stratosphere, and what it looks like there.
Of course, such studies have been conducted for a long time. So, in the USSR back in 1976, microorganisms were brought from heights of 48-77 kilometers. But the Japanese Aerospace Agency (JAXA) is so remarkable that it constantly invents curious projects for fairly reasonable money.
The fact is that usually such studies rely on the cultivation of extracted samples in the laboratory. We sow, grow, analyze what has grown. The problem, however, is thatmore than 99% of terrestrial microorganisms are uncultivated . They do not know how to grow in the laboratory. Accordingly, 99% of species diversity with this approach from the "catch" is lost.
The Japanese circumvented this difficulty by simply examining all the extracted samples with a fluorescence and scanning electron microscope. And although their balloon brought microbes from relatively “modest” heights of 13-27 km, this is the first estimate of the density of all (including uncultivated) microorganisms in the stratosphere.
Unfortunately, during the flight, they managed to claimp oteryat test (negative control) cell. For what reason are they planning to repeat the launch in June 2017, combined, if I heard correctly, with a genetic analysis of the extracted microorganisms.
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SURVIVABILITY OF RNA AND PROTEIN MONOMERS AGAINST EFFECTS OF SHOCK PRESSURES
Suppose a meteorite with Earth DNA crashes into another planet. Explosion, pressure surge, instant heating. Will organics survive this adventure? To find out, the authors shot artificial “meteorites” with an admixture of proteins and ribonucleic acids at targets and measured how much organics would survive after the impact. It turns out not very much:
Does this mean that panspermia is not working? Of course not. You can come up with a lot of more gentle methods of delivering organics by meteorites. But, in any case, a direct, airless blow “on the forehead” against a body the size of Mars seems to be fatal even for relatively simple organic molecules.
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PULMONARY INFLAMMATORY RESPONSES TO ACUTE METEORITE DUST EXPOSURES - IMPLICATIONS FOR HUMAN SPACE EXPLORATION
This topic is not new. I still read somewhere in the 95th year that lunar dust is very harmful to the lungs and causes severe silicosis in laboratory rats.
In this work, we studied the inflammatory stress response of the human lung tissue to lunar, Martian, West and earth dust. The first three are extracted from meteorites from the corresponding bodies, the last from earth basalts.
The observations are disappointing. All types of dust have a very noticeable and bad effect on the lungs. But the most evil dust is Martian, it is comparable in effect to earthly mine sludge, from which people are seriously ill. Behind it is the moon dust. Milled earth basalts showed the least harmfulness, although, of course, they are not honey either.
[Picture from the described work. Stress response of lung tissue to different types of dust. Image Credit: AD Harrington, FM McCubbin, J. Kaur, A.Smirnov, K. Galdanes, MAA Schoonen, LC Chen, SE Tsirka, T. Gordon / NASA Johnson Space Center; Dept. of Environmental Medicine, New York University School of Medicine; Dept. of Geosciences, Stony Brook University; Geology Dept., Lone Star College; Environmental Sciences Dept., Brookhaven National Laboratory; Pharmacological Sciences, Stony Brook University]
Conclusions? Firstly, if people ever set foot on Mars, they will have to seriously protect themselves from dust (so my stack of sheets of noted inaccuracies and comments on the “Martian” was replenished with one more item). Secondly, we generally sometimes underestimate the role of dust in planned long-term expeditions. Moon dust, for example, has a terrible abrasive ability, leading to the rapid killing of moving mechanisms and rubbing surfaces. If you are curious, I advise you to read at least the last paragraph on the fifth page of this document .
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CLIMATE OPTIMUM ON MARS INITIATED BY ATMOSPHERIC COLLAPSE
Today's Mars is dry and perfectly sterilized. But it is reliably known that once upon a time there happened at least one episode of warming, with a warm, thick atmosphere and liquid water, from which the riverbeds were preserved. How long, how long, and what caused this favorable climate? Here various hypotheses begin.
One of them was put forward in the paper in question. Pretty funny, like "the fire was caused by a fire engine that arrived on a fake call." It states that the warming period was a response to the first collapse of the atmosphere. Which caused the release of huge quantities of methane, previously stored in soil in the form of methane clathrates.. The products of oxidation and photolysis of this methane caused a strong greenhouse effect and warming. Was it really so, I can’t judge. But the hypothesis is interesting.
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DRIVEN BY EXCESS? CLIMATIC IMPLICATIONS OF NEW GLOBAL MAPPING OF NEAR-SURFACE HYDROGEN ON MARS
Working with complex findings, which I mostly did not make out. I remember a simpler initial premise.
The authors constructed an updated map of the hydrogen content in the surface layers of Mars using data from a Mars Odyssey neutron spectrometer. And it turned out that the ice content in the first decimeters of the surface of Mars is at least several percent, even at the equator, reaching> 90% closer to the poles.
[Map of the hydrogen content (in terms of water) in the first decimeters of the surface of Mars. Image Credit: AV Pathare; WC Feldman; TH Prettyman; S. Maurice / Planetary Science Institute, Tucson, AZ; IRAP, Université Paul Sabatier, Toulouse, France]
Of course, ice on Mars has long been found. But it seems that there are several times more there than previously thought.
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CAN MARS BE TERRAFORMED?
The short answer is no.
Detailed answer: in principle, it is possible to come up with a lot. But the most straightforward project is unlikely to work. Its essence is that by evaporating enough carbon dioxide CO 2 from the Martian polar caps, it would be possible to strengthen the greenhouse effect to such an extent that the climate on Mars will become warm and self-sustaining.
However, having carried out an audit of the CO 2 reserves on Mars according to the most recent data, the authors came to the same conclusion that I received more crude methods in 2006. Namely, carbon dioxide reserves on Mars are not enough to implement this scenario; and even the evaporation of all the polar caps will warm the planet only by about 10 degrees, which is not enough to switch to a self-sustaining warm mode.
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EFFICIENCY OF ATMOSPHERIC EROSION BY IMPACTS: ENERGY CONSIDERATIONS AND APPLICATIONS
First, there is such a thing as Shuvalov’s parameters. These are formulas that relate the effectiveness of the "scattering" of the atmosphere by an asteroid falling onto the planet with the parameters of the asteroid and atmosphere:
Secondly, this efficiency has a maximum. A meteorite too large or too fast has a worse atmospheric “stripping” efficiency than its smaller counterpart:
[Atmospheric ablation efficiency as a function of the Shuvalov parameter ξ. Image Credit: Shuvalov, V., 2009. Meteorit. Planet Sci. 44, 1095-1105.]
Thirdly, by choosing asteroids of maximum efficiency, one can calculate how many of them will be needed to “disrupt” most of the atmosphere of Venus. Answer: a lot. Unrealistic a lot. We are talking about masses in (0.5-9)% of the mass of the moon. The upper limit of this estimate exceeds the mass of the asteroid belt. It can be roughly estimated that the kinetic energy required to reject such an asteroid breakthrough is at least ~ 10 27 Joules, which is a million times higher than the annual energy budget of mankind.
Thus, projects to terraform Venus by “blowing” its atmosphere remain, at best, science fiction.
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OCEANUS: A Uranus Orbiter Concept Study from the 2016 NASA / JPL Planetary Science Summer School
Electronic Poster
Pros: NASA finally decided to come up with the concept of a serious expedition to Uranus. With access to orbit and a landing probe.
Cons: everything is very preliminary. Students are engaged in this. It is not known what class the mission will be, and this radically determines the budget, financial, mass, and general layout of the station. Therefore, several very different concepts are being worked out simultaneously in parallel. The launch, if it takes place, is not until the year 2030, with the arrival of Uranus in the 2040s. In general, if I manage to survive and get lucky with health, then perhaps it will still be interesting to me.
Update: at the NASA briefing, however, wider work was announced on this topic (a picture from the video briefing, not from the work in the title), so perhaps everything will turn out to be somewhat more optimistic:
--- === ---
A GEOPHYSICAL PLANET DEFINITION
From a geophysical point of view, Pluto and all fairly large bodies like Titan, Europe or Ganymede are full-fledged planets. When describing them, most of the features inherent in “real” planets are mentioned (equilibrium spherical shape, differentiation, tectonic activity, atmosphere, features of surface renewal and formation processes, thermal history). In the textbooks of planetology, Pluto or Ganymede are more naturally and logically described in the same section as Mars and Venus than with small asteroids. The language used to describe Pluto is much closer to "Martian" than to "cometary . " Finally, the authors cite more than 40 scientific papers from refereed journals, where Titan and Europe are mentioned precisely as planets.
And all this does not depend on whether "has cleared the body its orbit."
Therefore, the authors of the work suggest "stop the disgrace" with dwarf planets and, without waiting for permission (which is not required) from the International Astronomical Union, to begin, finally, simply call all these bodies planets.
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Planetary Topography from Laser Altimetry
Lecture on laser altimeters around other planets. General education and interesting. But in English, of course, nothing can be done. The first part of the video is the distribution of elephants and congratulations; for a lecture you need to rewind to the 16th minute.
--- === ---
NASA Headquarters Briefing
Another video. NASA executives report on progress, lost budget, and future plans. Minutes from the 51st begin with questions from the public, where, among other things, NASA is seriously going to reduce the cost of researching the Earth, climate, and human impact on the latter.
--- === ---
That's it. Thanks for attention!
After reading a couple of hundred reports and poster presentations, here I want to share a summary of the works that seemed interesting.
Disclaimer I am a physicist by training, but still not a specialist in planetology. My selection of material is probably subjective and incomplete. My interpretation of the work may be erroneous. If for you such things as finances, work, or professional reputation depend on its accuracy, then it is better to contact the authors and double-check everything with them directly. Their contacts are indicated in the abstracts of the works under the links. Corrections from readers are, of course, welcome.
So let's go!
TRANSIENT BROAD SPECULAR REFLECTIONS FROM TITAN'S NORTH POLE The
glint of the Sun in the lakes of Titan has been photographed for quite some time:
[Sunlight on Titan. Image Credit: NASA]
However, recently, such reflections have begun to be noticed where no lakes exist. Moreover, they are inconsistent. Today it sparkles, in the next flight with a very similar geometry - no longer. What's the matter?
To explain the hypothesis of "wet asphalt." Imagine that a methane rain passed over a slightly rough terrain. Asphalt gets wet and glitters. By the next passage of the Cassini over the terrain, it has dried up and reflections are no longer observed:
--- === ---
METHANE, ETHANE AND NITROGEN LIQUID STABILITY ON TITAN Let's
continue about the hydrosphere of Titan. Developed, with seas and rivers. True, the prefix "hydro" is not entirely appropriate here, because there is no water in those seas, but they are filled with liquid methane (CH 4 ), ethane (C 2 H 6) and nitrogen (N 2 ). It is not very clear only in what proportions and how these substances generally interact under the conditions of Titanium. What is the work about? It’s quite a laboratory.
The authors took these three gases, cooled them to cryogenic temperatures, and began to watch how they mix and when they freeze, depending on concentrations and pressures. And they discovered things in the light of which the hydrosphere of Titan looks like a much more complex system compared to the oceans on Earth. However, if instead of one you have three “waters” and three different ice, then something like this was to be expected.
The methane-ethane mixture freezes in more severe frost than each of the gases individually. That is, these gases work as mutual antifreezes.
When this mixture freezes, methane ice floats to the surface, while ethane ice sinks and falls to the bottom. Which is formed first - depends on the initial concentration.
[Photo of an experimental camera from work. On the left is ethane ice at the bottom of the liquid mixture. On the right is methane on its surface. Image Credit: J. Hanley, L. Pearce, G. Thompson, W. Grundy, H. Roe, G. Lindberg, S. Dustrud, D. Trilling, S. Tegler / Lowell Observatory, Flagstaff, AZ; Northern Arizona University, Flagstaff, AZ; University of Texas, Austin, TX.]
Further, the ingress of nitrogen into the mixture (simply from the atmosphere) can increase the melting point of the mixture and, accordingly, lead to its unexpected freezing. By the way, in another worknitrogen has been shown to dissolve well in methane - but poorly in ethane. Thus, the evaporation of a part of methane from a liquid can cause a sudden “boiling” of the sea. A kind of cryogenic champagne with nitrogen bubbles.
Finally, the most interesting. At pressures of more than 2.5 atmospheres (corresponding to depths of more than ~ 100 meters on Titan), the methane-ethano-nitrogen mixture is divided into two liquid phases. The report was an amazing video, here you have to limit yourself to a not-so-good picture:
[Image Credit: J. Hanley, L. Pearce, G.Thompson, W. Grundy, H. Roe, G. Lindberg, S. Dustrud, D. Trilling S. Tegler / Lowell Observatory, Flagstaff, AZ; Northern Arizona University, Flagstaff, AZ; University of Texas, Austin, TX.]
Above is gas. Below it is the first liquid phase rich in ethane. Under it is a second, rich in nitrogen. And on the “ceiling” of the first phase, a tiny hint of a droplet is visible. This is a condensate of the second phase. Which with real drops, like oil in water, flows through the light of the first into the second.
Have you imagined two-layer seas? So do I.
After the report, I thought about something else. The terrestrial oil industry has long been engaged in the cryogenic separation of associated gases. Of which the very first are methane and ethane. Well, nitrogen and the atmosphere is full. So, perhaps, with all these interesting effects in oil refining people are already familiar. It is difficult not to pay attention to the suddenly frozen (from the ingress of nitrogen) pipeline. But if this is so, then surely all these studies are deeply closed corporate secrets ...
--- === ---
CLASSIFICATION OF LABYRINTH TERRAINS ON TITAN The
labyrinths of Titan are plateaus cut by a complex system of valleys and ridges that visually resemble the bark of a tree:
[Image Credit: NASA / JPL]
Their nature is not quite clear. At first glance, they look like river beds - and we know that there are rivers on Titan. But, looking more closely, you can see that some of these "labyrinths" are closed. They do not "flow" from nowhere.
So, at least part of the labyrinths is not a channel? The authors took up morphological analysis and concluded that some of these formations are supposedly ... karsts ! But what exactly gives rise to them — whether dissolution of material by underground flows, flushing or evaporation — remains unknown.
Are not the labyrinth plains on Titan made of similar scourges?
--- === ---
TOPOGRAPHIC ASSESSMENT OF HOLLOWS ON MERCURY: DISTINGUISHING AMONG FORMATION HYPOTHESES
Since we are talking about karsts , it makes sense to transfer to Mercury. Mysterious pits ("hollows") on it have not yet been properly explained. But one hypothesis claims that it ... is also karst. Formed by the evaporation of some volatile substance under a layer of dust and regolith.
This is what they look like:
[Pits on Mercury. Yes, one should try to see holes in these spots, not ledges, and concave craters in rounded tubercles. Sometimes a rotated picture helps, so I added one. Image Credit: NASA]
We do not know what this material is. And I don’t even know if the hypothesis is true. In this work, I just liked the pictures. Good, beautiful photographs of the "pits" collected by the authors in order to classify them and presented to the public. The numbers I wrote down. And the authors forgive me, I laid out one, slightly taking photos to raise the contrast. In my defense, I note that the pictures on the presentation also looked much better than the originals from the MESSENGER website.
[Image Credit: NASA / JPL]
--- === ---
OXYGEN DEPLETION ON THE SURFACE OF MERCURY: EVIDENCE OF SILICON SMELTING?
After spending 4 years in orbit around Mercury, the MESSENGER device was able to measure the content of the main mineral-forming elements (O, Si, Ti, Al, Cr, Fe, Mn, Mg, Ca, Na, K, S, Cl) in the surface of the planet.
True, the device only sees the concentration of atoms, and not the chemical bonds between them. To evaluate the mineral composition, all metallic elements are usually assumed to be completely oxidized. That is, silicon, for example, is present as SiO 2 , aluminum as Al 2 O 3, and the like. Of the obtained oxides, then, as from the constructor, minerals are composed (for example, calcium silicate Ca 2 SiO 4 is 2 * CaO + SiO 2 ).
Everything would be fine, but only for Mercury it does not work. The oxygen balance does not converge. It turns out to be insufficient to oxidize everything that is oxidized, while maintaining the measured ratio of oxygen to silicon O / Si = 1.4 ± 0.03 (and even less, as stated in the work).
In an attempt to explain this discrepancy, a hypothesis was put forward: a kind of “metallurgical smelting” of pure silicon from quartz and graphite takes place in the depths of Mercury, which, as we strongly suspect, accounts for several percent of the planet’s crust.
If this is true, then 12.6–17.9% (by weight) of the surface of the northern hemisphere of Mercury should be formed by metallic silicon or its alloy with iron.
Why is this interesting? Well, firstly, unoxidized silicon as a rock-forming substance is unusual. Secondly, on all other rocky bodies (Moon, Earth, Mars) there is an excess of oxygen and everything that, in principle, can be oxidized by it, has been oxidized for a long time. Why is this suddenly not the case on well-sun-fried Mercury? The riddle.
[Mercury and silicon. Left Image Credit: NASA / JPL; Right Image Credit: Wikipedia]
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LUNAR CRUSTAL MAGNETIZATION INFERRED FROM CHARACTERISTICS OF LUNAR SWIRLS
I thought that I knew a lot about the Moon. But, as it turned out, he was not aware of the existence of “ lunar diffuse structures ” ( lunar swirls ). Moreover, I can’t even imagine what the official name of this phenomenon is in Russian. On the Internet there are “vortices”, “turbulences”, “curls”, “albedo anomalies” and “diffuse structures”. The latter, although less often, but in more serious sources, so I will use this term.
Opened back in the 1960s, these structures still represent a mystery. Outwardly, they look like light stripes and spots, with a kind of periodic pattern:
[Lunar diffuse structures. Left Image Credit: Wikipedia; Right Image Credit: NASA]
This pattern vividly reminded me of the pictures that appear on an electron beam TV when a magnet is presented, if anyone remembers this phenomenon. This similarity is reflected in one of the hypotheses explaining diffusion structures. It is believed that under them in the lunar soil lie natural permanent magnets. Say, a magnetized lava tube or the remains of an iron meteorite. With their magnetic field, they deflect energetic charged particles of the solar wind, not allowing them to bombard the surface - and therefore it remains light. A kind of invisible protective dome over the terrain. By the way, these structures are indeed associated with magnetic anomalies.
The work itself is about evaluating the parameters of a buried magnet, but I already had enough surprise.
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HOW DIELECTRIC BREAKDOWN MAY WEATHER THE LUNAR REGOLITH
Not only meteorites plow the lunar surface. It turns out that the solar wind, especially on a moonlit night, makes a quite comparable contribution. How? A stream of energetic electrons. Which can fly to the night side of the Moon and charge there regolith particles to tensions of ~ 10 6 V / m. Which leads to explosive electrical breakdown. The material in the breakdown channel evaporates, adding gas to the rarefied lunar atmosphere, and the dust particle is destroyed or re-melted. Soil, as a result, is slowly mixed up. This works the better, the darker and colder the terrain (in heat, the charge "flows" with normal conductivity).
So, who knows, maybe the traces of the astronauts will not be erased not by dust from a meteorite falling nearby, but by gradual evaporation from trillions of microscopic electrical breakdowns?
[Also electric discharge, but larger]
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SPACECRAFT IMPACTS ON THE MOON: CHANG'E 1, APOLLO LM ASCENT STAGES
Electronic poster
Cosmonautics already has its own archeology. Looking at modern orbital images of planets, people find there devices that reached these celestial bodies decades earlier (see, for example, the magnificent story about Mars-3 ).
The author of this work specializes in traces of the fall of the lunar apparatus, collecting a whole collection of them. This year, four more were added to them: from the take-off steps of Apollo 12 and -14, the Chinese Chang'E 1, and, more recently, from the European SMART-1.
[Traces of the fall of the takeoff stage of Apollo 12. Image Credit: NASA / Philip J. Stooke] It was
slightly surprised (besides the topic itself) that many falls left behind not craters at all, but strokes and stripes. Apparently, speeds of 1 km / s and below are not enough for explosive destruction of the apparatus or soil, and sliding contact simply leads to the scattering of debris over a long distance along the direction of the orbit.
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SIZE AND SOLAR INCIDENCE DISTRIBUTION OF SHADOWS ON THE MOON
It is hard to believe that the Moon, already examined for more than half a century along and across, in 30-centimeter resolution "photographed from the face and back", covered with 180 tons of human debris , may still hold something else mysterious. Yes, and in such a banal, it would seem, things like shadows.
And yet.
The authors took up a simple and seemingly boring activity. They began to study the size distribution of moon shadows. Statistics in its purest form. But not obvious. After all, a shadow is a complicated thing. With a "gliding" morning incidence of rays, the characteristics of the terrain depend extremely non-trivially.
And dug up. The density of shadows with sizes of 3-100 meters, firstly, does not depend on their size, and secondly, does not have a clear explanation. So, there is something like this in the distribution of the bumps of the lunar surface on these scales, which we do not yet understand. People at the conference asked smart questions, compared something with the distribution of crater sizes, were surprised, but I won’t take it now.
It would seem that the golem statistics of black and white spots, but brought to mind - and it turns out that another mystery lies on the long-studied moon. Somewhere in a deep shadow ...
[Picture from work. Image Credit: Oded Aharonson, Paul O. Hayne, Norbert Schorghofer]
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PENITENTES AT TARTARUS DORSA, PLUTO
Calgaspores (they are also penitentes, penitentes) - beautiful and unusual fields of snow-ice needles:
[Kalgaspory. Image Credit: Wikipedia]
[Calgaspore. Image Credit: Wikipedia]
Until now, they were known only on Earth. But, according to the latest data, it seems that they are also found on Pluto.
Of course, no one saw them there. But the authors of the work argue that these long stripes in the photograph “are well described by theoretical models of calgospores, and their interval, orientation, and growth rates are in good agreement with observations of New Horizons methane ice on Pluto.”
[Pluto, region of Tartarus Dorsa. Image Credit: NASA / JHUAPL / SWRI]
And yes, most likely the Pluto calgaspores consist of methane (CH 4 ) ice.
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BISMUTH TELLURIDES AND SULFIDE MIXTURES AND THEIR RELATION TO METAL FROST ON VENUS
Something quite reminiscent of snow can be seen on the radar images of the Venusian hills. But, of course, at 500 degrees Celsius this should be something else. Something with high reflectivity and high dielectric constant. Perhaps almost metallic in nature. What exactly?
["Snow" in the Maxwell Mountains on Venus. Image Credit: NASA / Magellan]
The authors suggested that these are tellurides or mixed bismuth sulfides ( Bi 2 Te 3 , Bi 2 Te 2 S) Having recreated Venusian under laboratory conditions, they watch how these substances are sublimated and interact with the atmosphere. Trying, in particular, to understand whether they, like earthly snow, will settle in the Venusian mountains in the 300-degree "frost" there.
The conclusions are mixed, and in general the work did not seem to me particularly convincing. Assumptions and alternative explanations are visible even to a layman. But the imagination of this "semiconductor snow" spurs, and therefore leave it on the list.
[Bismuth sulfide telluride, it is tetradimite. Image Credit: Wikipedia]
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THE BIOPAUSE PROJECT: BALLOON EXPERIMENTS FOR SAMPLING STRATOSPHERIC BIOAEROSOL
Those who read the Kraitonovsky Strain of Andromeda will immediately appreciate the charm of this research. The idea is the same: to get closer to outer space, “scoop up” life from there and bring down for study. In order to understand how far earthly life extends into the stratosphere, and what it looks like there.
Of course, such studies have been conducted for a long time. So, in the USSR back in 1976, microorganisms were brought from heights of 48-77 kilometers. But the Japanese Aerospace Agency (JAXA) is so remarkable that it constantly invents curious projects for fairly reasonable money.
The fact is that usually such studies rely on the cultivation of extracted samples in the laboratory. We sow, grow, analyze what has grown. The problem, however, is thatmore than 99% of terrestrial microorganisms are uncultivated . They do not know how to grow in the laboratory. Accordingly, 99% of species diversity with this approach from the "catch" is lost.
The Japanese circumvented this difficulty by simply examining all the extracted samples with a fluorescence and scanning electron microscope. And although their balloon brought microbes from relatively “modest” heights of 13-27 km, this is the first estimate of the density of all (including uncultivated) microorganisms in the stratosphere.
Unfortunately, during the flight, they managed to claim
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SURVIVABILITY OF RNA AND PROTEIN MONOMERS AGAINST EFFECTS OF SHOCK PRESSURES
Suppose a meteorite with Earth DNA crashes into another planet. Explosion, pressure surge, instant heating. Will organics survive this adventure? To find out, the authors shot artificial “meteorites” with an admixture of proteins and ribonucleic acids at targets and measured how much organics would survive after the impact. It turns out not very much:
Impact pressure - (corresponding speed) -% preservation:
10.5 GPa - (~ 2.2 km / s) - 4.3%
28 GPa - (~ 4 km / s) - 0.7%
40 GPa - (~ 6 km / s) - 0 %
Does this mean that panspermia is not working? Of course not. You can come up with a lot of more gentle methods of delivering organics by meteorites. But, in any case, a direct, airless blow “on the forehead” against a body the size of Mars seems to be fatal even for relatively simple organic molecules.
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PULMONARY INFLAMMATORY RESPONSES TO ACUTE METEORITE DUST EXPOSURES - IMPLICATIONS FOR HUMAN SPACE EXPLORATION
This topic is not new. I still read somewhere in the 95th year that lunar dust is very harmful to the lungs and causes severe silicosis in laboratory rats.
In this work, we studied the inflammatory stress response of the human lung tissue to lunar, Martian, West and earth dust. The first three are extracted from meteorites from the corresponding bodies, the last from earth basalts.
The observations are disappointing. All types of dust have a very noticeable and bad effect on the lungs. But the most evil dust is Martian, it is comparable in effect to earthly mine sludge, from which people are seriously ill. Behind it is the moon dust. Milled earth basalts showed the least harmfulness, although, of course, they are not honey either.
[Picture from the described work. Stress response of lung tissue to different types of dust. Image Credit: AD Harrington, FM McCubbin, J. Kaur, A.Smirnov, K. Galdanes, MAA Schoonen, LC Chen, SE Tsirka, T. Gordon / NASA Johnson Space Center; Dept. of Environmental Medicine, New York University School of Medicine; Dept. of Geosciences, Stony Brook University; Geology Dept., Lone Star College; Environmental Sciences Dept., Brookhaven National Laboratory; Pharmacological Sciences, Stony Brook University]
Conclusions? Firstly, if people ever set foot on Mars, they will have to seriously protect themselves from dust (so my stack of sheets of noted inaccuracies and comments on the “Martian” was replenished with one more item). Secondly, we generally sometimes underestimate the role of dust in planned long-term expeditions. Moon dust, for example, has a terrible abrasive ability, leading to the rapid killing of moving mechanisms and rubbing surfaces. If you are curious, I advise you to read at least the last paragraph on the fifth page of this document .
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CLIMATE OPTIMUM ON MARS INITIATED BY ATMOSPHERIC COLLAPSE
Today's Mars is dry and perfectly sterilized. But it is reliably known that once upon a time there happened at least one episode of warming, with a warm, thick atmosphere and liquid water, from which the riverbeds were preserved. How long, how long, and what caused this favorable climate? Here various hypotheses begin.
One of them was put forward in the paper in question. Pretty funny, like "the fire was caused by a fire engine that arrived on a fake call." It states that the warming period was a response to the first collapse of the atmosphere. Which caused the release of huge quantities of methane, previously stored in soil in the form of methane clathrates.. The products of oxidation and photolysis of this methane caused a strong greenhouse effect and warming. Was it really so, I can’t judge. But the hypothesis is interesting.
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DRIVEN BY EXCESS? CLIMATIC IMPLICATIONS OF NEW GLOBAL MAPPING OF NEAR-SURFACE HYDROGEN ON MARS
Working with complex findings, which I mostly did not make out. I remember a simpler initial premise.
The authors constructed an updated map of the hydrogen content in the surface layers of Mars using data from a Mars Odyssey neutron spectrometer. And it turned out that the ice content in the first decimeters of the surface of Mars is at least several percent, even at the equator, reaching> 90% closer to the poles.
[Map of the hydrogen content (in terms of water) in the first decimeters of the surface of Mars. Image Credit: AV Pathare; WC Feldman; TH Prettyman; S. Maurice / Planetary Science Institute, Tucson, AZ; IRAP, Université Paul Sabatier, Toulouse, France]
Of course, ice on Mars has long been found. But it seems that there are several times more there than previously thought.
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CAN MARS BE TERRAFORMED?
The short answer is no.
Detailed answer: in principle, it is possible to come up with a lot. But the most straightforward project is unlikely to work. Its essence is that by evaporating enough carbon dioxide CO 2 from the Martian polar caps, it would be possible to strengthen the greenhouse effect to such an extent that the climate on Mars will become warm and self-sustaining.
However, having carried out an audit of the CO 2 reserves on Mars according to the most recent data, the authors came to the same conclusion that I received more crude methods in 2006. Namely, carbon dioxide reserves on Mars are not enough to implement this scenario; and even the evaporation of all the polar caps will warm the planet only by about 10 degrees, which is not enough to switch to a self-sustaining warm mode.
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EFFICIENCY OF ATMOSPHERIC EROSION BY IMPACTS: ENERGY CONSIDERATIONS AND APPLICATIONS
First, there is such a thing as Shuvalov’s parameters. These are formulas that relate the effectiveness of the "scattering" of the atmosphere by an asteroid falling onto the planet with the parameters of the asteroid and atmosphere:
Secondly, this efficiency has a maximum. A meteorite too large or too fast has a worse atmospheric “stripping” efficiency than its smaller counterpart:
[Atmospheric ablation efficiency as a function of the Shuvalov parameter ξ. Image Credit: Shuvalov, V., 2009. Meteorit. Planet Sci. 44, 1095-1105.]
Thirdly, by choosing asteroids of maximum efficiency, one can calculate how many of them will be needed to “disrupt” most of the atmosphere of Venus. Answer: a lot. Unrealistic a lot. We are talking about masses in (0.5-9)% of the mass of the moon. The upper limit of this estimate exceeds the mass of the asteroid belt. It can be roughly estimated that the kinetic energy required to reject such an asteroid breakthrough is at least ~ 10 27 Joules, which is a million times higher than the annual energy budget of mankind.
Thus, projects to terraform Venus by “blowing” its atmosphere remain, at best, science fiction.
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OCEANUS: A Uranus Orbiter Concept Study from the 2016 NASA / JPL Planetary Science Summer School
Electronic Poster
Pros: NASA finally decided to come up with the concept of a serious expedition to Uranus. With access to orbit and a landing probe.
Cons: everything is very preliminary. Students are engaged in this. It is not known what class the mission will be, and this radically determines the budget, financial, mass, and general layout of the station. Therefore, several very different concepts are being worked out simultaneously in parallel. The launch, if it takes place, is not until the year 2030, with the arrival of Uranus in the 2040s. In general, if I manage to survive and get lucky with health, then perhaps it will still be interesting to me.
Update: at the NASA briefing, however, wider work was announced on this topic (a picture from the video briefing, not from the work in the title), so perhaps everything will turn out to be somewhat more optimistic:
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A GEOPHYSICAL PLANET DEFINITION
From a geophysical point of view, Pluto and all fairly large bodies like Titan, Europe or Ganymede are full-fledged planets. When describing them, most of the features inherent in “real” planets are mentioned (equilibrium spherical shape, differentiation, tectonic activity, atmosphere, features of surface renewal and formation processes, thermal history). In the textbooks of planetology, Pluto or Ganymede are more naturally and logically described in the same section as Mars and Venus than with small asteroids. The language used to describe Pluto is much closer to "Martian" than to "cometary . " Finally, the authors cite more than 40 scientific papers from refereed journals, where Titan and Europe are mentioned precisely as planets.
And all this does not depend on whether "has cleared the body its orbit."
Therefore, the authors of the work suggest "stop the disgrace" with dwarf planets and, without waiting for permission (which is not required) from the International Astronomical Union, to begin, finally, simply call all these bodies planets.
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Planetary Topography from Laser Altimetry
Lecture on laser altimeters around other planets. General education and interesting. But in English, of course, nothing can be done. The first part of the video is the distribution of elephants and congratulations; for a lecture you need to rewind to the 16th minute.
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NASA Headquarters Briefing
Another video. NASA executives report on progress, lost budget, and future plans. Minutes from the 51st begin with questions from the public, where, among other things, NASA is seriously going to reduce the cost of researching the Earth, climate, and human impact on the latter.
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That's it. Thanks for attention!