Journey Through The Solar System, Episode 08 - Life On Mars
Transcript
00:00In the continuing search for life, two Viking spacecraft were launched by the Lewis Titan
00:25and Centaur rockets to land on Mars in 1976.
00:34I'm Larry Ross, Director of Space Programs at NASA's Lewis Research Center in Cleveland,
00:39Ohio.
00:40This is the 8th program in our 13-program series called Journey Through the Solar System.
01:10During this program, we will see two NASA films made about the unmanned Viking missions.
01:33The first film is called Mars, Is There Life? and was made before the landings.
01:39The second film was made after the landings.
01:42Please watch carefully to see how our knowledge expands.
01:46The second film actually corrects some of the first film's predictions.
02:03In the distant past, it may have begun like this for a very young planet called Mars.
02:09It was an age of volcanic activity.
02:19With volcanoes came their gases, including water vapor.
02:24These gases condensed and formed rain.
02:27In its beginning, it rained for countless years.
02:31The rain cooled the planet's surface.
02:41The rain eventually formed streams.
02:44These cut channels in the planet as the waters flowed over the terrain.
03:10The waters continued to grow larger in size.
03:14The oceans widened.
03:16Small streams emptied into larger ones, creating rivers or oceans.
03:22This is the past history of Mars as some see it.
03:27This is Mars today.
03:32The once powerful volcanoes of Mars appear to be extinct or dormant today.
03:38Calcium and erosion have covered their once molten lava with a mantle of dust.
03:44Yet volcanoes are still present, and larger than any on Earth.
03:54Olympus Mons is the largest known volcano in the solar system.
03:59It is three times higher than Mount Everest.
04:13Mars also has a system of canyons.
04:20The U-shaped walls indicate that rock slides and avalanches have helped shape them.
04:27Four times deeper than the Grand Canyon, these canyons might be 150 miles wide.
04:36They may extend over a distance of 2,000 miles.
04:42What forces could have formed these canyons, and when?
04:59And what about the water that once apparently filled these eroded channels?
05:05Once these may have been rivers or tributaries.
05:08Today the water is gone, leaving behind dried up riverbeds.
05:16What happened to the water?
05:18When did it disappear?
05:20And what removed it?
05:28The water that may still exist on Mars is probably located in part at the poles,
05:34existing as polar ice or frost.
05:38It is joined there by frozen carbon dioxide in temperatures of minus 190 degrees Fahrenheit.
05:46This is the coldest place on the surface of Mars.
06:06Although water appears to be frozen in the ice caps, and although it may exist in the
06:11crust as permafrost, there is relatively little water on Mars.
06:16Mostly this is a planet covered with dust, and the dust is moved by winds.
06:24Usually the Martian dust storms last only a few days, but they carry dust up to speeds
06:30of 250 to 300 miles per hour.
06:39The dust storms have apparently contributed to much of the erosion that has taken place
06:44on Mars.
06:46The dust storms have helped shaped mountains, volcanoes, and other surface features.
06:53At times, the dust has even appeared to have formed dunes.
07:10So Mars is not without Earth-like features, although portions of its surface are pitted
07:16with impact craters.
07:30If Mars is so seemingly desolate, apparently covered with little water or oxygen, what
07:37could live here today?
07:40Further, how can we determine if life presently exists on Mars?
07:58The answers on how to detect Martian life are found aboard the Viking lander that rests
08:03on the planet's surface.
08:06These cameras, with their mirrors, show us what is on the planet.
08:12Yet they are controlled from the Earth.
08:17Certain instruments measure the velocity of the winds and provide information on a variety
08:22of surface and subsurface conditions.
08:26After traveling 440 million miles for nearly one year, one of the most important things
08:34this craft must do is to reach into the Martian soil and return a sample to the lander.
08:41This would be an easy task on Earth, but on Mars, machines must act as our hands.
09:11Returning the soil to the Viking lander is the first step in searching for the answer
09:22to a question that can change man's way of thinking.
09:26This desolate planet, if it has life, could alter the thought that Earth alone has living
09:33creatures upon it.
09:36So the journey of the soil back to the lander is one of great importance.
09:44Once the material reaches the spacecraft, it is sifted as it falls through an opening
09:49into the interior of the lander.
09:51Some of the material falls into a chamber where it can be tested for the presence of
09:57life in a biology experiment.
10:01In this chamber, the soil is moistened with a liquid that includes food that Earth microorganisms
10:06thrive on.
10:08A sample of the Martian atmosphere is pumped into the chamber and then the weight.
10:15If there are microorganisms acting upon the food in the soil, it will give off a gas.
10:22The gas will mix with the Martian atmosphere, and when it is analyzed by chemical detectors,
10:28it may reveal that life is present.
10:36While the first experiment is taking place, some of the soil is also falling into another
10:41chamber for a second biology experiment.
10:48This time the soil is also moistened with nutrients, but the nutrients are tagged with
10:54radioactive carbon-14.
10:58If the organisms are in the soil sample, they will feed on the nutrients and pass the
11:04radioactive carbon off with their gases.
11:07The gases can later be analyzed by other equipment aboard the lander, and the presence of radioactive
11:13carbon will indicate the presence of life.
11:21In the third and final biology experiment, a sample of the soil has fallen into a third
11:27chamber where it receives a small amount of moisture and an atmosphere of carbon dioxide
11:32gas tagged with radioactive carbon-14.
11:37Simulated Martian sunlight is introduced, and if plant-like organisms are present in
11:42the soil, they will capture the carbon-14.
11:46Later the original carbon-14 gas will be flushed out of the container, and the chamber will
11:53be heated to over 1,000 degrees Fahrenheit.
11:57If there is carbon-14 in the soil sample, it will be detected when released in the heating
12:03process.
12:05This would indicate plant-like organisms existing on Mars.
12:11But what life exists on Mars today?
12:16Could there be creatures like those that abound on Earth?
12:21Exactly what forms of life could exist on Mars?
12:51The biology experiments are designed for the very small organisms, partially because
13:08of their abundance and their ability to survive environmental extremes.
13:13The Martian planet abounds with mysteries, from its volcanoes to its bleak landscape.
13:22We know this place only from a great distance.
13:26Its secrets are there for us to discover.
13:30But if we do not find life on Mars today, it may mean we just looked in the wrong places
13:37or searched with the wrong instruments or came at the wrong time.
13:44But if we do find life on Mars today, it will mean that life on Earth is not an isolated
13:50instance, and it will offer further evidence that we are not alone in the universe.
14:00There were high hopes that the Viking missions might find clear evidence of life, but the
14:05findings were not clear, as we will see in a NASA film called 19 Minutes to Earth.
14:14It was not just another day on the planet Mars.
14:18A spacecraft had successfully landed and was monitoring this unique planet.
14:24The information was transmitted, and it took 19 minutes to reach Earth.
14:30Even from the beginning of the Viking mission to Mars, we began to assemble more than just
14:35pictures of the Martian surface.
14:38As information was received, we began to piece things together and to understand a place,
14:45a planet other than our own.
14:52As the planet was orbited, we began to understand Mars through a series of incredible photographs,
14:58photographs that, when assembled, told of the planet's history.
15:04We found remarkable evidences of running water.
15:09Here are just a few of what appear to be dried-out riverbeds.
15:23Although other evidence states that liquid water could not flow on Mars today, we can
15:28that at one time in the past, liquid water must have flowed on the Martian surface.
15:34When did this take place, and was there life on Mars when these channels were filled with
15:40water?
15:44We now know where part of the Martian water is today, and that is in the permanent polar
15:50cap.
15:51Previously thought to be frozen carbon dioxide, we now have evidence that the permanent polar
15:56cap is largely composed of water ice.
16:01Here you can see channels formed through melting of this ice.
16:13Other photographic evidence reveals a closer look at the Martian Grand Canyon, a system
16:18of huge canyons extending for 2,000 miles across the planet.
16:25What forces caused the surface to split apart in so many places?
16:36This raises the question as whether Mars is dynamic and active.
16:41Is it similar to Earth in that its volcanoes erupt lava on the surface?
16:47The evidence is clearly seen that Martian volcanoes have erupted in the past, and from
16:52this mission, we know that at least one quake has taken place recently on Mars.
16:58So Mars is alive, and we now have a general idea of the thickness of its crust.
17:16Further evidence of volcanic activity in the past is seen from the surface, where a variety
17:22of volcanic rocks are pitted with gas pockets, and sharp or angular in appearance.
17:46These rocks face the day-to-day environment of Mars, and obviously, many have been reduced
17:52in part to the Martian dust.
17:54Let's examine the Martian environment as told to us through the Viking mission.
17:59To begin, the temperature.
18:03The temperatures appear to vary the same day-to-day, starting as an approximate low average temperature
18:09of 190 degrees Kelvin just before the Martian dawn.
18:13The temperatures rose to an average upper temperature of 240 degrees Kelvin.
18:20This temperature range appeared day-in and day-out relatively the same, almost to the
18:25point of monotony.
18:26Next, the atmosphere.
18:27The extremely thin upper Martian atmosphere consists of some familiar gases.
18:40The most abundant is carbon dioxide, a gas that we breathe out.
18:50Another is carbon monoxide, dangerous to life as we know it, argon, oxygen in small
19:00amounts, atomic oxygen, nitric oxide, and a small but significant amount of nitrogen.
19:13Additional argon and nitrogen data reveals that Mars once had a much denser atmosphere,
19:18which could have supported running water.
19:21An analysis of the Martian soil shows an iron-rich clay with an unusually high amount of sulfur.
19:28The elements that make up this clay are familiar.
19:32Carbon, silicon, magnesium, aluminum, calcium, and sulfur.
20:00In terms of abundance, silicon and iron are in the largest amounts.
20:06Silicon is also one of the most abundant elements in the Earth's crust.
20:13Magnesium, aluminum, calcium, and sulfur exist in significant amounts.
20:19The soil samples appear to be very similar in composition at the two different sites
20:24on Mars, but nowhere were organic carbon compounds found in the soil.
20:30The absence of organic carbon compounds affects the interpretation of the three biology experiments
20:37conducted on the surface of Mars.
20:40One experiment used a sample of Martian soil moistened with a liquid that included foods
20:46that Earth microorganisms thrive on.
20:53A sample of the Martian atmosphere was pumped into the chamber, and if there were microorganisms
20:59in the soil, the gases given off would later be detected, possibly indicating the presence of life.
21:12Let's take a look at the results of this experiment.
21:15If there is life, the gases should vary over the days shown.
21:45This data does not exclude the possibility of life, but neither does it strongly support it.
22:15The second biology experiment involved another sample of Martian soil,
22:19also moistened with a liquid containing nutrients.
22:26But this time the nutrients were tagged with radioactive carbon-14.
22:32If the organisms were in the soil sample, they would have taken in the nutrients
22:37and passed off radioactive carbon with their gases.
22:43The gases, when analyzed, would have indicated the presence of life.
22:49Let's take a look at the results of this experiment.
22:53The soil samples behaved remarkably similar at both landing sites on Mars.
22:58Here is a graph of the results at one landing site,
23:01and here is the graph of the same experiment at the other landing site.
23:06The similarity is remarkable, showing a reliable experiment,
23:10and the immediate change from radioactive carbon dioxide to carbon monoxide
23:16strongly suggests the presence of life, although there are non-biologic explanations.
23:23Still, let's compare this experiment conducted on Antarctic soil
23:29to that on Martian soil.
23:35By itself, you can see this experiment could favor the presence of life,
23:40but remember the first experiment, no organic carbon compounds,
23:45and finally our third experiment.
23:48In the third and final biology experiment, a sample of the soil was placed in a chamber
23:53where it received a small amount of moisture and an atmosphere of carbon dioxide gas
23:58tagged with radioactive carbon-14.
24:02Simulated Martian sunlight was introduced,
24:05and if plant-like organisms were present in the soil, they would capture the carbon-14.
24:11Later, the original carbon-14 gas was flushed out of the container,
24:16and the chamber was heated to over 1,000 degrees Fahrenheit.
24:20If there was carbon-14 in the soil sample,
24:23it would have been detected when released in the heating process.
24:27This would indicate plant-like organisms existing on Mars.
24:33Let's examine the results and see if life was indicated by this experiment.
24:40First, the data itself.
24:44Let's take a look at this information as shown on a graph.
25:02From this information and supporting evidences,
25:05we cannot conclusively say that life is or is not present in the Martian soil.
25:11With certainty, if life does exist on Mars, it most likely is in relatively few numbers.
25:18One final discovery in the Martian mission dealt with its moons.
25:23An extremely close flyby of Phobos has given us information that could lead to invaluable data
25:29concerning the origin and evolution of the entire solar system.
25:33Are the Martian moons captured asteroids?
25:37And are they slowly being pulled apart by the Martian gravity?
25:42While this mission has answered many questions, it has raised still others.
25:48We do not yet have conclusive evidence on whether or not some form of life exists on Mars.
25:54Some data support the possibility that Martian life could conceivably exist.
26:00The Mars atmosphere includes all the basic materials needed for life,
26:05including nitrogen, carbon, oxygen, and water vapor.
26:10Mars ice caps contain much water.
26:13Summertime daylight temperatures at the equator are about 80 degrees Fahrenheit.
26:19But there are also data that are contrary to the notion that Martian life could exist.
26:25The atmospheric pressure is only about 1% that of Earth,
26:29a pressure that would cause animal blood to boil.
26:33Water would vaporize instantly in the thin atmosphere.
26:37There is not enough ozone in the Martian atmosphere to block life-damaging radiation.
26:43Temperatures at the Mars equator fall to as low as 150 degrees below zero at night.
26:50Clearly, more study is needed to see if life exists on Mars,
26:55or if it once existed and perished there.
26:58Scientists envision an unmanned robot, a surface rover,
27:02to be sent to Mars to drive to secluded valleys to search and probe for life.
27:08This Mars rover would weigh about 220 pounds.
27:12Other proposals are to collect and return samples of Mars soil to orbiting Earth laboratories for analysis.
27:20Next time, we will take a look at Jupiter, the next planet beyond Mars in our solar system.
27:26Until then, this is Larry Ross saying goodbye from NASA's Lewis Research Center in Cleveland, Ohio.
27:57NASA Jet Propulsion Laboratory
28:01California Institute of Technology