life as a drug dealer and police officer. criticize police a lot and when i criticize, i'm talking about the bad police. the overwhelming majority of cap's are doing their job but you hear about the tamir rice cases, you hear about the bad and once law enforcement starts weeding them out, because every time you see one of these cases, you look at the person's background, seven complaints for use of force, five substantiated. and then we don't find out until they kill somebody. nationalithsonian's air and space museum opened 40 years ago. july 1, 1976. leading up to the anniversary, american history tvs real america is showing a series of nasa films.

up next from 1979, planet mars documents the search to a understand our earthlike planet. the film includes an overview of the flybys of the red planet between 1964, 1971. also, the viking mission that landed two craft in 1976. ♪

narrator: of all the planets in the solar system, earth and mars are the most similar. despite the similarities, mars is essentially like no other planet. it is an unique world. it was elusive to astronomers for hundreds of years. through telescopes, it appeared to be a small, red sphere. it was estimated to be half the size of earth. one of the earliest known representations of the planet drawn in 1659 indicating markings on the surface. the movement of the dark patches across the surface indicated that mars rotated on its axis about 24 and one half hours.

it was observed to that the tilt of its access exposed to the polar regions ultimately to the sunlight. each hemisphere has a summer and winter period. one martian year and each of its seasons is almost twice as long as earth. later mappings of the planet has made dark and light regions as continents and oceans. the landmass is read as the sandstone of earth. the water is a greenish blue. in 1877, an italian astronomer

discovered channels, resembling the finest threads of a spider's web drawn across the disk. in america, an observatory was founded to study to martian features. massive irrigation systems, designed to carry water from icecaps to the remnants of a dying civilization. science-fiction writers populated the city with terrible creatures. they had skills beyond earth man's dreams. in the 1960's, a spacecraft flew by mars and photographed about 10% of the surface. gone were the canals, gone were the cities. the photographs revealed a cratered landscape, much like the moon. it was regarded as hostile to life. in 1971, the spacecraft orbited

mars. it transmitted more than 7000 photographs of the planet to earth. the extensive mapping revealed a new and unexpected world. the southern hemisphere was flattened and gouged by the impact of media rights. the northern hemisphere was a -- meteor rights -- meteorites. the northern hemisphere was a vast plain with few craters. the plateau that joins this is cut by a vast and deep canyon. it is channeled with the terroristic -- characteristic patterns of stream channels on earth.

then in 1975, two viking spacecraft was launched. each were programmed to drop a robot on the surface of mars. one of its principal objectives was to detect the presence of learning organisms. the communication system in pasadena, california. on june 19, 1976, the first viking arrived after a journey of 400 million miles. once in orbit, its cameras were turned to a detailed examination of the landing area.

imaging teams covered a territory the size of texas. the chosen landing site had a few impact craters, one of the lowest regions on the surface. on july 20, 1976, flight controllers ordered the separation from the orbiter. because of the great difference between mars and earth, the signal traveling at the speed of light took 19 minutes to reach the spacecraft. this necessitated a completely automated instrumentation on board for carrying out the landing. during the landing, instrument analyzed the properties of the thin martian atmosphere. >> good roll, latitude hold.

>> -105. in sync. >> prepare for separation. >> 188 feet per second. [inaudible] >> 73 feet per second. >> acs is close to vertical. >> i have is green for touchdown. touchdown. we have touchdown. >> fantastic! [applause]

>> we have a touchdown time of 12 hours, 12 minutes. zero decibel, one second. >> job well done. i am assuming we must be sitting right on the x. that is the smooth area. everyone inside here could not be more pleased. thank you. [applause] narrator: 25 seconds after landing, one of the two cameras was initiated and scanned the first pictures of the martian surface. >> about half an hour later, when it started to come back and we got the first seven lines on the tv monitors you can see gray , and white levels. they knew there was something there. >> fantastic. >> all of a sudden we were

, looking at the surface of mars, and it was clear and not dusty. it was sharp. when we got to the end of that first picture, the dust and the small pebbles in the foot paths. it was just -- it was really a miracle. narrator: in an instant, it was wiped off tv monitors. behind it came the second picture. it was a long, panoramic view. it disclosed a section of the basin.

covered with sand and littered with rocks. the following day, viking sent back the first color picture. a find red or yellow dust covered the ground. 45 days after these historic events, viking to landed in area north of the first landing site. it took ventures of sites that were produced by volcanic processes or meteor impact. the lander conducted experiments on the surface. the orbiter continued to swing around the planet, marrying -- measuring moisture and temperature. it took high-resolution photographs of the martian terrain. ♪ narrator: four and a half billion years ago, the planets were formed from the gas and

dust of the solar nebula. from the formation of the planet, heat was released. because the heat can't escape as rapidly as it is growing, a point is reached when the interior melts. on mars, a lighter material rose to form the crust of the surface, which ended -- contains ice and other condensation. a later stage occurred, when molten rock melted the ice, causing a flurry of rock and dust across the surface. some believe that such a process may be the construction of those major channels on the surface of mars, seen today. others believe that among its first billion years, the atmosphere may have been warm and dense enough for rain to fall and rivers to flow. gradually, the original warm blanket of the atmosphere evolved into the thin, dry carbon dioxide atmosphere we find there today. because of the low atmospheric temperature, water cannot exist in liquid form.

it must either freeze or evaporate. while there are no oceans or rivers on mars, there is more water than was expected. the residual polar cap to the north is water and ice mixed with dust.

the measurements of water vapor over the planet suggest that there is a vast reservoir of ice under the surface. one can think of the residual polar cap as the tip of an iceberg, protruding from a sea of rock. at lower atmospheres, rock swirls around the slopes of martian volcanoes. to the south, in the canyons and valleys, there is frequently a haze seemed to evaporate in the morning, as the sun warms the atmosphere. on earth, the oceans' heat and moisture interact with air currents to produce complex weather patterns. on mars, due to a lack of great water, the weather doesn't very much from day-to-day. like remote weather station honored, vikings meteorology instrument measures the

atmospheric pressure, wind and wind direction. temperatures range from -100 degrees fahrenheit, just after dawn, to -22 degrees in the midafternoon. light winds from the east change to light winds from the south after midnight. maximum wind speed is 15 miles per hour. in the early summer, the heating of dust particles in the air creates violent dust storms. driven by wind that reach 150 miles an hour, they may blanket the entire planet in just a few days.

>> in order to understand the geology and physics of windblown particles on mars, we are conducting a series of experiments used in this enormous chamber at our nasa research center. we placed an open wind tunnel in the channel and art able to operate under atmospheric surface pressures on mars. in this particular series of experiments, we have placed a model in the tunnel floor and want to determine the zone of erosion and deposition around the crater.

in this particular case, we are going to let the wind blow across the crater and see what those zones of erosion and deposition around it. i like -- deposition around it are like. narrator: that is the most common feature around mars on the surface related to wind. it is followed from the global dust storms. the region in which the light layer of material reveals a darker surface. these streaks serve as wind markers. the patterns define the wind flow. to the geologist, the features seen in tens of thousands of photographs transmitted by the viking show what has shaped the surface of mars. the excavation of large craters and basins by asteroids and meteorites. the raising of mountains through the action of volcanoes. the folding and subsiding of the crust at the planet expanded.

the cutting of channels by water, or the abrasive particles carried by the wind over tens of millions of years. the key to the age and sequence of the features is found in the number and condition of the craters. those areas with fewest craters are assumed to be the youngest. here, a fresh crater overlays an ancient, eroded one. here, it is eroded by water or wind. craters that have been buried to varying depths. over millions of years, the repeated flows of lava build the volcanic mountains of mars.

12 are larger than any on earth. the largest rises three times higher than mount everest and is broad enough to cover all of the volcanoes that cover the hawaiian islands. the great gash that cuts through mars plus equatorial is up to 400 miles wide, and it can drop four miles below the cratered surface. canyon walls are delayed. extending for 30 miles on the canyon floors are sand dunes, suggesting some of the debris caused by the collapse of canyon walls was removed by wind.

these ancient channels that resemble dry riverbeds on earth could have been formed by wind storms. but the vast channel system and collapsed terrain, extending hundreds of miles across the low lands, and teardrop shaped islands above the channel bed testify to a process without any parallel on earth. viking also photographed the two cratered moons of mars. phobos, the inner moon. and deimos, the smaller, outter moon. viking could observe boulders on the moon's surface. the study of the surface indicates that mars has experienced periodic change of climate. the best evidence is seen in the strange solar patterns of mars.

the dark bands are buried ground within the north polar ice cap. on each scar are numerous small terraces, indicated by eroded small rock. this is an area of terrain about 40 miles across. it is believed the large scars represent two different cycles of climate change, which occur simultaneously. because of mars' osceolation around the sun, it is alternately warm in cold for tens of thousands-millions of years. during the cold time, mixtures of dust and ice were deposited in a series of near-horizontal layers, obscuring the underlying typography.

then, a time of warmer climate followed and erosion set in. cutting deep valleys into the icy mass of the polar caps. after the erosion cycle, new layers were laid down. another episode of erosion followed.

this oblique truncating of one set of terraces obscure few gated by another indicates the climactic change turns on and off. it is the first evidence of climactic change on a planet other than the earth. the speculation about changes in the atmosphere and climate are closely related to the notion that life in some form might exist on mars. on earth, life developed several billion years ago, at a time when the overall properties of mars and the earth were very similar. >> over billions of years, mars and the earth evolved separately. however, mars today still has chemicals on its surface and atmosphere, temperatures, and pressures, in which we believe life can exist. the viking lander was equipped with three life detection experiments determined to test for chemical changes, caused by life processes familiar to us on earth.

on earth, all living organisms organize with the environment is a process called catalyst them. narrator: on earth, carbon dioxide is released into the environment by life forms. green plants and some microorganisms do the reverse in the process of photosynthesis. they remove carbon dioxide and using sunlight as an energy source can change the carbon dioxide into organic matter and release oxygen into the atmosphere. >> if the mars experiments indicated they were doing the same, then we can assume the possible existence of organisms on the planet. our results on mars in certain experiments gave us data which seem to mimic the metabolism of living organisms. however, careful analysis indicates it is probably the result of chemical rather than biological processes.

narrator: on earth, all biological systems are based on organic compounds. -- chemistry. it was believed that life on mars would be based on organic compounds. the notion strengthened when experiments on earth demonstrated organic materials can be formed under simulated martian conditions. >> we used finely powdered minerals, like those expected on the martian surface, and then we added traces of radioactive water vapor and carbon dioxide at low pressure. to simulate martian sunlight, we used an arc lamp. one we heeded the sample and captured the gases our radiation , counter showed that the carbon monoxide in the water had been converted into organic compounds.

narrator: viking's instruments failed to detect organic compounds of any kind. that fact in the opinion of some observers, increase the odds against the existence of living organisms on mars. >> if we were able to do 1000 experiments on mars, and to do these in a wide variety of places on mars, in the canyons, on the polar caps, in some deep areas of the surface, and if in all of these experiments we got negative results, then the answer to the question, is there life on mars would almost certainly be no. but on the basis of just a few experiments, done on just two sites on the planet, it would be unscientific for us to come to that conclusion.

all we can really say for sure is that we have run across some very interesting chemistry, the kind of chemistry we do not see in surface samples of the earth or from the moon. that is about where we are at the moment. today, in laboratories across the nation, scientists are trying to simulate the results we obtained on mars. some of the scientists are concentrating on the radiation experiments to see whether solar energy acting on mars could have produced chemicals to account for the results. other experiments are assuming these chemicals were there, and are testing one or another of these chemicals to see whether the same results can be attained. ♪

narrator: the question of life on mars is only one of the inexhaustible number of questions for which we seek to gain answers in space. questions about the origin and evolution of the solar system, of our own planet, and our own species. the search for answers is a goal of planetary exploration and the journeys of all spacecraft to the near and far reaches of the solar system are beginning to provide some of the answers. ♪

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conventions to follow this summer. >> colorado. >> florida. >> texas. >> ohio. >> and the first non-politician in several decades. watch live on c-span, listen on the c-span radio app, or get video on demand at c-span.org. you have a front row seat to every minute of the conventions beginning on monday. >> he looks at the major political players in the u.s. and soviet union in the final years of the soviet war. an hour.ut