Curiosity 2013: lake, geology, radiation
Since June, Curiosity on the road, does not stop anywhere for more than a couple of weeks, does not conduct serious research, only crawls and crawls to Sharpe's mountain, slowly but surely. However, in the last part of the full-scale study of Yellowknifle Bay, he took with him a stock of mined soil from the Cumberland well, and periodically carried out analyzes on the road. NASA held a press conference where it told about the latest scientific results of the mission. They told about clay, potential organic matter, geological dating and radiation on the surface of Mars.
Before you begin your review, you need a little understanding of the Yellowknifle Bay stratigraphy. Let me remind you: stratigraphy is the science of layers. The surface that the Earth, that Mars, resembles a layer cake. The lowest, basic layer from which all the subsequent ones arose is called a crystalline basement in geology. Above, layers are laid out on the foundation that have arisen under the influence of various influences: asteroids and meteorites fall, water erosion, weathering, glacial erosion, layers formed by the activity of organisms, from stromatolites and limestones to the cultural layer left by man, are added on Earth.
We are only interested in a few meters of surface layers, since Curiosity can study them. To the surprise of NASA geologists, even these few meters turned out to be as diverse as no one expected.
')
In the lowlands of Yellowknifle Bay, geologists identified three main layers: the deepest and most interesting - clay Sheepbed;
(Note: he is red only because of covering dust, so his color is pale gray-blue.)
slightly higher - the “threshold” of the dense sandstone of Gillespie Lake;
and even higher dark rocks called Glenelg:
(This particular cliff was named Point Lake)
In Sheepbed, Curiosity drilled two wells, John Klein and Cumberland. Clay particles were found in both, but Cumberland showed an even higher water content. Taking with him a few portions of Cumberland clay, the rover went on the road, and geologists sat down for a long study of the data.
The analysis carried out by the SAM device showed the presence of water, oxygen, carbon dioxide, sulfur oxide, nitrogen oxide, hydrogen sulfide, hydrogen chloride in the soil. SAM studies only gases that are emitted from the soil when heated in a microwave or placed in a liquid solvent. A high carbon content may indicate the presence of hydrocarbon compounds, i.e. organics, but scientists emphasize that they cannot vouch for its Martian origin - perhaps they are traces of a solvent. In addition, organic compounds of non-biological origin were found in meteorites, so organic matter on Mars does not mean life, even past.
(Please note that some indicators have been increased to fit the graphics to one size).
Often, optimists who do not want to part with the hope of finding Martians, at least dead and microbiological, use the argument: "On the surface, all the organic matter was destroyed by radiation, it is necessary to drill a few meters and look there."
We have to think that not stupid people work at NASA, so they thought about it before sending a device with a 7-centimeter drill to Mars. Conducted preliminary studies and modeling of conditions gave such an interesting schedule:
From it becomes clear that at a 5-centimeter depth for 1 billion years, radiation will destroy all complex organic compounds like proteins. However, more primitive compounds with an atomic mass of less than 100 will be able to last longer — up to a billion and a half years. And among these compounds are some amino acids, alcohols and other simple organic compounds.
However, such subtleties were not even useful when scientists set an approximate date for the appearance of layers of Sheepbed on the surface. It turned out that the lowlands of Yellowknifle Bay are the result of wind erosion. This area has been destroyed for millions of years, and Cumberland appeared on the current surface of “only” about 80 million years ago. For geological history, this is not such a long time, and even more for such a calm planet like Mars.
It turns out that at first the Sheepbed layer was formed several billion years ago, then it was closed with new layers, and then, under the influence of changed conditions, the wind began to destroy the upper levels, gradually reaching deep clay:
This study allowed us to adjust future plans, and outlined new goals for the rover. Previously, scientists did not anticipate drilling operations until they approached Sharpe's Mount, but now they pointed to a new target called KMS-9.
They decided that the youngest surface, in which it makes sense to look for organic matter, is hidden under the “thresholds”, so they made out a suitable site just 600 meters ahead:
Curiosity will do this journey in about a couple of months.
Perhaps these changes to the plans are due to the fact that NASA is concerned about the state of the Curiosity wheels, which turned out to be too weak against the sharp stones of the Gale crater. Now on the tread of the front four wheels you can see a few holes and some are quite impressive:
However, while the damage is visible only on thin sheets, the thickness of which is 0.8 mm, the frame is much thicker and has not even cracked anywhere. Therefore, you shouldn’t worry much about the health of the rover - it will pass over a hard surface on a net cord, and he wasn’t going to the sands anyway. Moreover, NASA is constantly engaged in that changes plans, so you should not force it.
Let's continue about the radiation. Earlier, before the landing of Curiosity, scientists had very relative data obtained from satellites. MSL also carries on board the RAD radiation telescope, which meticulously records everything that falls on it from space. As it turned out, not too little is being rolled in, but not as much as it was previously thought:
It seems that surface conditions are only about two times better than in space, but do not forget that Curiosity made space measurements when it was inside the capsule, and on Mars itself it was practically “without a cap”. Of course, a few millimeters of aluminum, from which the first houses of Martian settlers will be, will not constitute a serious obstacle to cosmic rays, but the particles will already slow down the atmosphere, therefore the protective qualities of the dwelling will increase. But still, if the future landing modules will be two-story, it is better to equip the bedrooms on the first floor.
It is curious that the rover practically does not fix the effects of solar radiation, i.e. even a tiny atmosphere protects the planet. But from the interstellar cosmic rays its defense is weaker, but it is still inversely proportional to its thickness. What is even more fun is that during solar flares, the intensity of cosmic rays decreases, i.e. solar radiation displaces "enemy competitors" and covers the planet from radiation. The graph built for the first three hundred solov on the planet shows interesting patterns:
Variations in the intensity of radiation exposure occur due to fluctuations in atmospheric pressure. During the daytime, the surface and atmosphere heats up and rushes up and to the sides, moving to less warm areas, i.e. on the night side. It turns out that the daytime atmosphere is more voluminous, but less dense and it is easier for the cosmic particles to pass through. Night cold atmosphere is thinner, but denser, and, thus, better protects against radiation. It turns out that the most "protected" time on the surface of Mars is about 8 am, and the most "radioactive" is the evening after 4:00 pm:
As can be seen from this graph, the time of the year also plays an important role. True, all these fluctuations of radiation exposure are within 10%, so that it is better not to refuse lead underwear.
On the hundredth sol, the rover covered a light dust storm, and it was interesting for me to see how the dust hanging in the atmosphere would affect the radiation, and for sure: a decrease in the intensity of space bombardment is observed for several solos. So that future colonists should remember: you can walk in the morning and in a storm. But it is better, even on Earth to think about how to replenish the atmosphere of Mars.
Let us return to the results of the study of samples Cumberland.
The obtained data, even during the preliminary study, allowed to say that the name Yellowknifle Bay was prophetic, and the rover actually turned out to be at the bottom of the bay, although it was dry. The composition of the soil corresponds to the bottom sediments of a freshwater lake:
Moreover, all the conditions indicate that the lake was fully adapted to the habitat of chemolithotrophic microorganisms, i.e. those that extract energy from mineral compounds, rather than sunlight or the absorption of their own kind.
Of course, most of the media immediately seized on this idea, and some directly stated that microbes lived there. Although, in fact, scientists have only confirmed what they said back in the spring.
Unfortunately, another event that is of great importance for science and further study of the entire solar system, passed almost unnoticed. Curiosity for the first time, for interplanetary missions, produced geological dating by the radioisotope potassium-argon method !
The resulting value gave the lake age of Cumberland 4.2 + -0.4 billion years. Preliminary dating of the crater, which was based on an analysis of the intensity of the surface meteorite bombardment, showed a value of 3.6–4.1 billion years:
The nature of the chemical composition of the soil Cumberland indicates that these particles were brought by the flow of water from the shaft of the Gale crater and deposited in the standing lake water.
Although the radioisotope method slightly aged the age of the crater, in general, the value turned out to be quite accurate. It is worth explaining that the early figure of 3.6 billion years did not come from the ceiling, but based on an estimate of the Late heavy bombardment assumed at that time. The bombardment was dated due to geological samples brought from the moon. Those. - watch your hands - Curiosity, having studied the ground from Mars, confirmed the reality of the landing on the moon. Well, and besides this, he confirmed the loyalty of the current theory of the evolution of the solar system and modern methods of dating of planets and satellites.
During my trip to the mountain, Curiosity saw many new breeds that can tell even more about the past of Mars, I look forward to some major conference where they will publish the results of these travel observations. And all this is just warming up. The most delicious is ahead:
1920x1200 Vk
NASA release
Publications in ScienceMag
PS Here Mars One announced the start of fundraising for the first private mission to Mars ...
Before you begin your review, you need a little understanding of the Yellowknifle Bay stratigraphy. Let me remind you: stratigraphy is the science of layers. The surface that the Earth, that Mars, resembles a layer cake. The lowest, basic layer from which all the subsequent ones arose is called a crystalline basement in geology. Above, layers are laid out on the foundation that have arisen under the influence of various influences: asteroids and meteorites fall, water erosion, weathering, glacial erosion, layers formed by the activity of organisms, from stromatolites and limestones to the cultural layer left by man, are added on Earth.
We are only interested in a few meters of surface layers, since Curiosity can study them. To the surprise of NASA geologists, even these few meters turned out to be as diverse as no one expected.
')
In the lowlands of Yellowknifle Bay, geologists identified three main layers: the deepest and most interesting - clay Sheepbed;
(Note: he is red only because of covering dust, so his color is pale gray-blue.)
slightly higher - the “threshold” of the dense sandstone of Gillespie Lake;
and even higher dark rocks called Glenelg:
(This particular cliff was named Point Lake)
In Sheepbed, Curiosity drilled two wells, John Klein and Cumberland. Clay particles were found in both, but Cumberland showed an even higher water content. Taking with him a few portions of Cumberland clay, the rover went on the road, and geologists sat down for a long study of the data.
The analysis carried out by the SAM device showed the presence of water, oxygen, carbon dioxide, sulfur oxide, nitrogen oxide, hydrogen sulfide, hydrogen chloride in the soil. SAM studies only gases that are emitted from the soil when heated in a microwave or placed in a liquid solvent. A high carbon content may indicate the presence of hydrocarbon compounds, i.e. organics, but scientists emphasize that they cannot vouch for its Martian origin - perhaps they are traces of a solvent. In addition, organic compounds of non-biological origin were found in meteorites, so organic matter on Mars does not mean life, even past.
(Please note that some indicators have been increased to fit the graphics to one size).
Often, optimists who do not want to part with the hope of finding Martians, at least dead and microbiological, use the argument: "On the surface, all the organic matter was destroyed by radiation, it is necessary to drill a few meters and look there."
We have to think that not stupid people work at NASA, so they thought about it before sending a device with a 7-centimeter drill to Mars. Conducted preliminary studies and modeling of conditions gave such an interesting schedule:
From it becomes clear that at a 5-centimeter depth for 1 billion years, radiation will destroy all complex organic compounds like proteins. However, more primitive compounds with an atomic mass of less than 100 will be able to last longer — up to a billion and a half years. And among these compounds are some amino acids, alcohols and other simple organic compounds.
However, such subtleties were not even useful when scientists set an approximate date for the appearance of layers of Sheepbed on the surface. It turned out that the lowlands of Yellowknifle Bay are the result of wind erosion. This area has been destroyed for millions of years, and Cumberland appeared on the current surface of “only” about 80 million years ago. For geological history, this is not such a long time, and even more for such a calm planet like Mars.
It turns out that at first the Sheepbed layer was formed several billion years ago, then it was closed with new layers, and then, under the influence of changed conditions, the wind began to destroy the upper levels, gradually reaching deep clay:
This study allowed us to adjust future plans, and outlined new goals for the rover. Previously, scientists did not anticipate drilling operations until they approached Sharpe's Mount, but now they pointed to a new target called KMS-9.
They decided that the youngest surface, in which it makes sense to look for organic matter, is hidden under the “thresholds”, so they made out a suitable site just 600 meters ahead:
Curiosity will do this journey in about a couple of months.
Perhaps these changes to the plans are due to the fact that NASA is concerned about the state of the Curiosity wheels, which turned out to be too weak against the sharp stones of the Gale crater. Now on the tread of the front four wheels you can see a few holes and some are quite impressive:
However, while the damage is visible only on thin sheets, the thickness of which is 0.8 mm, the frame is much thicker and has not even cracked anywhere. Therefore, you shouldn’t worry much about the health of the rover - it will pass over a hard surface on a net cord, and he wasn’t going to the sands anyway. Moreover, NASA is constantly engaged in that changes plans, so you should not force it.
Let's continue about the radiation. Earlier, before the landing of Curiosity, scientists had very relative data obtained from satellites. MSL also carries on board the RAD radiation telescope, which meticulously records everything that falls on it from space. As it turned out, not too little is being rolled in, but not as much as it was previously thought:
It seems that surface conditions are only about two times better than in space, but do not forget that Curiosity made space measurements when it was inside the capsule, and on Mars itself it was practically “without a cap”. Of course, a few millimeters of aluminum, from which the first houses of Martian settlers will be, will not constitute a serious obstacle to cosmic rays, but the particles will already slow down the atmosphere, therefore the protective qualities of the dwelling will increase. But still, if the future landing modules will be two-story, it is better to equip the bedrooms on the first floor.
It is curious that the rover practically does not fix the effects of solar radiation, i.e. even a tiny atmosphere protects the planet. But from the interstellar cosmic rays its defense is weaker, but it is still inversely proportional to its thickness. What is even more fun is that during solar flares, the intensity of cosmic rays decreases, i.e. solar radiation displaces "enemy competitors" and covers the planet from radiation. The graph built for the first three hundred solov on the planet shows interesting patterns:
Variations in the intensity of radiation exposure occur due to fluctuations in atmospheric pressure. During the daytime, the surface and atmosphere heats up and rushes up and to the sides, moving to less warm areas, i.e. on the night side. It turns out that the daytime atmosphere is more voluminous, but less dense and it is easier for the cosmic particles to pass through. Night cold atmosphere is thinner, but denser, and, thus, better protects against radiation. It turns out that the most "protected" time on the surface of Mars is about 8 am, and the most "radioactive" is the evening after 4:00 pm:
As can be seen from this graph, the time of the year also plays an important role. True, all these fluctuations of radiation exposure are within 10%, so that it is better not to refuse lead underwear.
On the hundredth sol, the rover covered a light dust storm, and it was interesting for me to see how the dust hanging in the atmosphere would affect the radiation, and for sure: a decrease in the intensity of space bombardment is observed for several solos. So that future colonists should remember: you can walk in the morning and in a storm. But it is better, even on Earth to think about how to replenish the atmosphere of Mars.
Let us return to the results of the study of samples Cumberland.
The obtained data, even during the preliminary study, allowed to say that the name Yellowknifle Bay was prophetic, and the rover actually turned out to be at the bottom of the bay, although it was dry. The composition of the soil corresponds to the bottom sediments of a freshwater lake:
Moreover, all the conditions indicate that the lake was fully adapted to the habitat of chemolithotrophic microorganisms, i.e. those that extract energy from mineral compounds, rather than sunlight or the absorption of their own kind.
Of course, most of the media immediately seized on this idea, and some directly stated that microbes lived there. Although, in fact, scientists have only confirmed what they said back in the spring.
Unfortunately, another event that is of great importance for science and further study of the entire solar system, passed almost unnoticed. Curiosity for the first time, for interplanetary missions, produced geological dating by the radioisotope potassium-argon method !
The resulting value gave the lake age of Cumberland 4.2 + -0.4 billion years. Preliminary dating of the crater, which was based on an analysis of the intensity of the surface meteorite bombardment, showed a value of 3.6–4.1 billion years:
The nature of the chemical composition of the soil Cumberland indicates that these particles were brought by the flow of water from the shaft of the Gale crater and deposited in the standing lake water.
Although the radioisotope method slightly aged the age of the crater, in general, the value turned out to be quite accurate. It is worth explaining that the early figure of 3.6 billion years did not come from the ceiling, but based on an estimate of the Late heavy bombardment assumed at that time. The bombardment was dated due to geological samples brought from the moon. Those. - watch your hands - Curiosity, having studied the ground from Mars, confirmed the reality of the landing on the moon. Well, and besides this, he confirmed the loyalty of the current theory of the evolution of the solar system and modern methods of dating of planets and satellites.
During my trip to the mountain, Curiosity saw many new breeds that can tell even more about the past of Mars, I look forward to some major conference where they will publish the results of these travel observations. And all this is just warming up. The most delicious is ahead:
1920x1200 Vk
NASA release
Publications in ScienceMag
PS Here Mars One announced the start of fundraising for the first private mission to Mars ...
Source: https://habr.com/ru/post/205440/
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