Terraforming Mars, Venus & Europa

A project inspired by Kim Stanley Robinson’s novel

 “Red Mars”

Written by:

Kai Dautzenberg

Tobias Birx

Frank Kirsch

Table of Contents

1.0 Introduction

2.0 Description of Mars, Venus and Europa

2.1 Mars

2.1.1 General data

2.1.2 Atmosphere

2.1.3 Relief

2.1.4 Missions to Mars

2.2 Venus

2.2.1 General data

2.2.2 Atmosphere

2.2.3 Relief

2.2.4 Missions to Venus

2.3 Europa

2.3.1 General data

2.3.2 Atmosphere

2.3.3 Relief

2.3.4 Missions to Europa

3.0 Terraforming

3.1 Terraforming in general

3.2 Terraforming plans for Mars, Venus and Europa

3.2.1 Mars

3.2.2 Venus

3.2.3 Europa

 4.0 Conclusion

 5.0 References

1.0 Introduction

This essay is concerned with the comparison of Mars, Venus and the Jupiter satellite Europa in terms of terraforming. These have been chosen because they are the would-be candidates for terraforming in our solar system.

To provide the reader with an objective point of view, general data is presented as well as atmospheric composition and surface features of each of the heavenly bodies.

To each of the planet chapters we added an overview of the missions that started to explore the specific bodies. In the same way, we listed the proposed terraforming methods.

These are the results of our scientific research that enabled us to draw our conclusion.

We hope to enrich your knowledge of the solar system and to give aid for your own scientific work and opinion.

2.0 Description of Mars, Venus and Europa

 2.1 Mars

 2.1.1 General Data

Mars is the fourth planet from the Sun. Different in size and mass, Earth and Mars are similar in various more essential respects. Mars average diameter is 6,780 km which is about half the size of Earth but nearly twice the diameter of the Moon. The bulk density of 3.9 g/cm3 is lower than Earth’s (5.5. g/cm3 ). Due to its solid core, Mars has no radiation belt or magnetic field. Mars’ total mass is one tenth of Earth’s and as a consequence Mars’ gravity is only 38 % as strong. The average surface temperature varies from  -125° C to +27° C.

Mars has two satellites that are irregularly shaped: Phobos and Deimos. Both are massively cratered.

Comparable to Earth, Mars has seasonal changes and a day-night cycle of 24 hours, 37 minutes and 23 seconds. The planet circles the Sun in 687 days. As a result, one year on Mars is twice as long as on Earth.

2.1.2 Atmosphere

Mars atmosphere is mostly composed of carbondioxide (95.3 %), nitrongen is present at 2.7 % and argon at 1.6 %. The rest consists of oxygen, carbon monoxide, water vapor and other trace constituents. On the grounds of this composition, Mars’ surface pressure is 1/100th of the mean surfeace pressure of the Earth. Additionaly, the atmospheric pressure changes with season and elevation on Mars.

In its atmospheric circulation Mars is again quite similar to Earth as a consequence of the other similarities. The planet also underlies seasonal climate changes.

2.1.3 Relief

Weathered basaltic rock and iron oxides give Mars its orange to brown colored appearance.

Referenced to the mean surface level, Mars’ topography is divided in southern cratered highlands 1 to 5 km over the datum and smooth northern lowlands 0 to 3 km below the datum. These lowlands make out 40 % of the overall surface. Another highland is the Tharsis rise, more than 3,000 km across, which reaches 10 km in elevation and supports several huge volcanic shields. The smaller Elysium rise is as much as 5 km higher than the surrounding lowland plains.

Mars beares the biggest mountain in our solar system. It is called Olympus Mons and covers the same area as the state of Arizona. Olympus Mons’ height is 15,900 m and the huge Volcanic shield is 600 km across.

Another fantastic feature of Mars consists in its canyon system dominated by Valles Marineris which is the largest and deepest in the solar system. The abyss’ length is 4000 km and the walls are 5 to 10 km high. Two more scaringly huge surface features are the basins within the southern highlands, Hellas and Argyre, that are 1,500 and 800 km across and 7 and 2 km deep, respectively.

Mars surface is still in motion. Winds and sandstorms keep on resurfacing the planet resulting in an immense sand dune system around the northern polar plateau.

2.1.4 Missions to Mars

Mariner 4

Launch Date: Nov. 28, 1964

Arrival Date: Jul. 14, 1965

End of Operation: Dec. 20, 1967

Overview

Mariner 4 was the first spacecraft to get a close look at Mars. Flying as close as 9,846 kilometers (6,118 miles), Mariner 4 revealed Mars to have a cratered, rust-colored surface, with signs on some parts of the planet that liquid water had once etched its way into the soil. In addition to various field and particle sensors and detectors, the spacecraft had a television camera, which took 22 pictures covering about 1% of the planet. Initially stored on a 4-track tape recorder, these pictures took four days to transmit to Earth.

Aims

The Mariner 4 mission was designed to meet three major objectives:

1. Study interplanetary fields and particles, including the Martian magnetic field, cosmic dust, cosmic rays, and the solar wind.
2. Take close-up images of Mars in hopes of discovering the geologic and atmospheric processes at work on the planet over the eons.
3. Provide experience in operating long-term interplanetary missions.

After Mariner 4 was well under way to Mars, an experiment was approved to study the effect of transmitting the spacecraft's radio signal through the Martian atmosphere just before the spacecraft disappeared behind the planet. This experiment would reveal much about the Martian atmosphere. In order to perform this experiment, the spacecraft's computer had to be reprogrammed from Earth. This engineering feat, pioneered on Mariner 4, has been greatly refined and repeated numerous times in later missions, both to enhance and to salvage.

Mariner 6&7

Launch Date: Mariner 6: Feb. 24, 1969 Mariner 7: Mar. 27, 1969

Arrival Date: Mariner 6: Jul. 31, 1969 Mariner 7: Aug. 4, 1969

Overview

Mariners 6 and 7 were identical teammates in a two-spacecraft mission to Mars. Launched 31 days apart on Atlas/Centaur rockets, the spacecraft arrived at their closest approach to Mars (3,430 kilometers, or 2,200 miles) just four days apart. They transmitted to Earth a total of 143 pictures of Mars as they approached the planet and 55 close-up pictures as they flew past the equator and southern hemisphere. The images, covering about 20% of the planet, revealed a surface quite different from Earth's moon, somewhat contrary to the impressions left by Mariner 4's images. Mariners 6 and 7 revealed cratered deserts, as well as depressions with no craters, huge concentrically terraced impact regions, and collapsed ridges. The spacecraft also studied the atmosphere and its chemical composition.

Aims

These spacecraft were designed specifically to concentrate on Mars. Better quality imaging was planned to give a more complete picture of the Martian surface to help in planning future missions to Mars to search for signs of life. And more images could be made since they could be transmitted to Earth at 2000 times the rate of Mariner 4's data transmission. Mariners 6 and 7 were also equipped to study the Martian atmosphere, including its composition, pressure, density, and temperature. The atmospheric study using radio occultation that Mariner 4 conducted as an afterthought was designed into the Mariners 6 and 7 missions. (Although, as with Mariner 4, the computers on board Mariners 6 and 7 could also be reprogrammed from the ground.) A celestial mechanics experiment was also included as a way to precisely measure the mass of Mars.

Mariner 9

Launch Date: May 30, 1971

Arrival Date: Nov. 14, 1971

End of mission: Oct. 27, 1972

Overview

Mariner 9 was the first spacecraft to orbit another planet. It carried an instrument payload similar to Mariners 6 and 7, but, because of the need for a larger propulsion system to control the spacecraft in Mars orbit, it weighed more than Mariners 6 and 7 combined. When Mariner 9 arrived at Mars, the atmosphere was so dusty that the surface was obscured. This unexpected situation made a strong case for the desirability of studying a planet from orbit rather than merely flying past. Mariner 9's computer was thus programmed from Earth to delay imaging of the surface for a couple of months until the dust settled. After 349 days in orbit, Mariner 9 had transmitted 7,329 images, covering over 80% of Mars' surface. The images revealed river beds, craters, massive extinct volcanoes, canyons (including the Valles Marineris, a system of canyons over 4,000 kilometers [2,400 miles] long), evidence of wind and water erosion and deposition, weather fronts, fogs, and more. Mars' tiny moons, Phobos and Deimos, were also photographed. The findings from the Mariner 9 missions underpinned the Viking program.

Aims

Mariner 9 was designed to continue the atmospheric studies begun by Mariners 6 and 7, and to map over 70% of the Martian surface from the lowest altitude (1500 kilometers [900 miles]) and at the highest resolutions (1 kilometer per pixel to 100 meters per pixel) of any previous Mars mission. An infrared radiometer was included to detect heat sources as evidence of volcanic activity. Mars' two moons were also to be analyzed. Mariner 9 more than met its objectives.

Viking 1

Launch Date: Aug. 20, 1975

Arrival Date: Jun. 19, 1976

Landing Date: Jul. 20, 1976

End of mission: Nov. 13, 1982 (Lander)  Aug. 17, 1980 (Orbiter)

Overview

The Viking Mars mission was performed by two spacecraft, Viking 1 and Viking 2, launched within a couple of weeks of each other. Each spacecraft consisted of an orbiter and a lander, which traveled attached together for nearly a year to reach Mars orbit. The orbiters then began taking pictures of the Martian surface, from which a landing site was selected. The landers then separated from the orbiters and soft landed. The orbiters continued imaging and, between Viking 1 and Viking 2, imaged the entire planet at what was then high resolution. The orbiters also conducted atmospheric water vapor measurements and infrared thermal mapping. The Viking 1 orbiter flew within 90 kilometers of Phobos to take images of this larger, inner moon of Mars. The Viking landers took full 360-degree pictures, collected and analyzed samples of the Martian soil, and monitored the temperature, wind direction, and wind speed. The Viking missions revealed further details of volcanoes, lava plains, huge canyons, and the effects of wind and water. Analysis of the soils at the landing sites showed them to be rich in iron, but devoid of any signs of life.

Aims

The primary aim of the Viking missions was to look for any evidence of life, current or past, in the Martian soil. Other objectives were to make high-resolution images of the entire surface and find out more about the structure and composition of the atmosphere and surface. The orbiters, in addition to their own primary data gathering tasks, also had the supporting role of scouting landing sites and relaying data from the landers back to Earth.

Viking 2

Launch Date:     Sep. 9, 1975

Arrival Date:       Aug. 7, 1976

Landing Date:    Sep. 3, 1976

End of mission: Apr. 11, 1980 (Lander)

                            Jul. 25, 1978 (Orbiter)

Overview

The Viking Mars mission was performed by two spacecraft, Viking 1 and Viking 2, launched within a couple of weeks of each other. Each spacecraft consisted of an orbiter and a lander, which traveled attached together for nearly a year to reach Mars orbit. The orbiters then began taking pictures of the Martian surface, from which a landing site was selected. The landers then separated from the orbiters and soft landed. The orbiters continued imaging and, between Viking 1 and Viking 2, imaged the entire planet at what was then high resolution. The orbiters also conducted atmospheric water vapor measurements and infrared thermal mapping. The Viking 2 orbiter flew within 22 kilometers of Deimos and took high-resolution pictures of this smaller of the two moons of Mars. Unlike the Viking 1 orbiter, the orbit of Viking 2 was inclined well above the equator so that it could better study the polar regions. The Viking landers took full 360-degree pictures, collected and analyzed samples of the Martian soil, and monitored the temperature, wind direction, and wind speed. The Viking missions revealed further details of volcanoes, lava plains, huge canyons, and the effects of wind and water. Analysis of the soils at the landing sites showed them to be rich in iron, but devoid of any signs of life.

Aims

The primary aim of the Viking missions was to look for any evidence of life, current or past, in the Martian soil. Other objectives were to make high-resolution images of the entire surface and find out more about the structure and composition of the atmosphere and surface. The orbiters, in addition to their own primary data gathering tasks, also had the supporting role of scouting landing sites and relaying data from the landers back to Earth.

Pathfinder

Launch Date: Dec. 2, 1996
Arrival Date:  Jul. 4, 1997
End of mission: Sep. 27, 1997

Overview

Mars Pathfinder demonstrated a number of innovative, economical, and highly effective approaches to spacecraft and mission design of a planetary landing mission. The second of the Discovery Program missions, development of the spacecraft and free-ranging surface rover was limited to 3 years and $150 million. No orbiter was used to scout a landing site and deliver the lander to the surface. Rather, the microrover, named Sojourner, was encased in a self-righting tetrahedral lander, which, in turn, was encapsulated in an aeroshell designed to withstand atmospheric entry. From Viking photos, a landing site had been pre-selected. Slowed in its descent by a system of parachutes and retro-rockets, the lander/rover then fell freely the last few hundred feet, bouncing on its inflated airbags over the Martian surface like a basketball. The airbags deflated, the petals of the lander opened, and the rover descended and began exploring and analyzing nearby rocks. The engineering design far exceeded expectations. Pathfinder's lander, named the Dr. Carl Sagan Memorial Station, operated nearly three times its design lifetime of 30 days, and the Sojourner rover operated 12 times its design lifetime of seven days.

Aims

The primary objective of Mars Pathfinder was to demonstrate a low-cost method of delivering a set of science instruments and a free-ranging rover to the surface of Mars. Science objectives were to characterize surface features and analyze the composition of the rocks and soil at the landing site and to photographically and with analytical instruments monitor atmospheric and weather conditions as they varied over the course of the mission.

Mars Global Surveyor

Launch Date:     Nov. 7, 1996

Arrival Date:       Sep. 11, 1997

Overview

Mars Global Surveyor is an orbiter designed to economically fulfill most of the mission objectives of the Mars Observer spacecraft, lost just before it was to go into Mars orbit in August 1993. Mars Global Surveyor was initially placed into a highly elliptical orbit, which is very fuel efficient to achieve. Gradually, using a technique called aerobraking, the orbit was made more circular as the spacecraft slowed itself by barely skimming the upper Martian atmosphere as it made its closest approach to the planet each orbit (periapsis). Although this technique takes time, it saves greatly on fuel required for orbit trim maneuvers. After achieving a nearly circular, two-hour polar orbit with a highest altitude of about 450 kilometers (about 280 miles), Mars Global Surveyor began high-resolution mapping of the surface, as well as operating science data-gathering experiments. Its orbit allows it to map the entire planet every 7 days.

Aims

Mars Global Surveyor's mission is to map the entire planet at high resolution, and gather data on the surface morphology, topography, gravity, weather and climate, surface and atmospheric composition, and planetary magnetic field. It will also provide relay communications for future Mars missions, such as the Deep Space 2 Mars Microprobes.

Mars Climate Orbiter:

Launch Date: Dec. 11, 1998 13:45:51 EST

Status: Mission Lost - Sept. 23, 1999

Overview

Mars Climate Orbiter was launched in December 1998 and was scheduled to arrive at Mars in September 1999. Its mission was to use atmospheric instruments and cameras to provide detailed information about the surface and climate of Mars. As it prepared to enter orbit around Mars, the spacecraft was targeted too close to the surface, and either burned up in the atmosphere, or continued past the planet into space.

Aims

Mars Polar Lander

Launch Date:Jan. 3, 1999 15:21:10 EST
 

Arrival Date: Dec. 3, 1999

Overview

Mars Polar Lander, launched in January 1999, was to be the first-ever landing in the polar regions of Mars, near the southern polar cap. As of Dec. 7, 1999, however, no word has been received from the Lander, although flight controllers continue to search for it. The lander is equipped with cameras, a robotic arm and instruments to measure the composition of Martian soil. Two small microprobes--the Deep Space 2 technology mission--hitched a ride to Mars on the lander, with the goal of penetrating into the Martian subsurface to detect water ice.

Aims

New Millennium Deep Space 2

Launch Date: Jan. 3, 1999 15:21:10 EST
Arrival Date: December 3, 1999

Overview

The Mars Microprobe Mission, also known as Deep Space 2 (DS2), is the second deep-space technology-validation mission in NASA's New Millennium Program. The two DS2 microprobes hitched a ride to Mars aboard the Mars Polar Lander. The mission goal is to test key technologies for 21st-century network missions, in which multiple landers released from a single spacecraft will carry out comprehensive observations of dynamic, complex phenomena such as climate systems and seismic activity. However, as of Dec. 7, 1999, no word has been received from the Probes, although flight controllers continue to search for them. The New Millennium microprobe technologies enable a wide range of scientific studies that would not be affordable using conventional technologies.

Aims

Scientific Objectives

Mars 2001 Orbiter

Launch Date: Mar. 30, 2001
Arrival Date: Oct. 20, 2001

Overview

The Mars Surveyor 2001 Orbiter is scheduled for launch on March 30, 2001. It will arrive at Mars on Oct. 20, 2001, if launched on schedule. The 2001 Orbiter will be the first to use the atmosphere of Mars to slow down and directly capture a spacecraft into orbit in one step, using a technique called aerocapture. It will then reach a circular mapping orbit within about 1 week after arrival.

Aims

The '01 Orbiter will map the mineralogy and morphology of the Martian surface. It will also map the elemental composition of the surface and the abundance of hydrogen in the shallow subsurface, over the entire planet. In addition, the 2001 Orbiter will support communication with the '01 Lander and Rover.

Mars 2001 Lander/Rover

Launch Date: Apr. 10, 2001
Arrival Date: Jan. 22, 2002

Overview

The Mars '01 Lander will survey conditions for human exploration. It will arrive near the end of summer in Mars' southern hemisphere. The Lander will carry an imager to take pictures of the surrounding terrain during its' rocket-assisted descent to the surface. The descent imaging camera will provide images of the landing site for geologic analyses, and will aid planning for initial operations and traverses by the rover. It will carry a rover vehicle, which actually was the understudy for Sojourner, the rover carried by the Mars Pathfinder mission in 1997.

Mars Express

Launch Date: June 2003
Arrival Date: Late December 2003

Overview

The European Space Agency (ESA) and Agenzia Spaziale Italiana (ASI, the Italian space agency) plan to launch Mars Express, which will explore the atmosphere and surface of Mars from polar orbit. The spacecraft will carry a remote observation payload with some heritage from European instruments lost on the ill-fated Russian Mars 96 mission, as well as a lander communications package to support Mars lander missions from 2003 to 2007. It includes an option for a 60 kg surface lander.

Aims

2.2 Venus

 2.2.1 General Data

Venus is the second planet from the sun. Its distance to the center of the solar system is 108,208,930 km. Depending on Venus’ and Earth’s position in the orbit the distance between the two planets is 42,000,000 to 258,000,000 km. Venus is as old as all the planets in the inner solar system.

Venus has often been called Earth’s sister planet. But only Venus’ mass and size are similar to Earth’s, which do not play an important role due to the fact that these data are related to each other and of course mass and density depend on each other as well as volume and radius. Venus’ mass is 4.8690 x 1027 g, which is 80% of the Earth’s mass. The density values of both planets are even closer as with 5.2 g/cm³ for Venus and 5.52 g/cm³ for Earth. Provided that the Earth has a volume of 1, Venus has 0.88 or 88%. The mean equatorial radius finally reaches Earth’s by 94.88% with 6,051.8 km. Another comparable feature is the two planets’ interior. Both have an iron core and a molten rock mantel. Accordingly, Venus gravity is about 88% of Earth’s. Here the similarities end.

A sidereal rotation period of 243 earth days in retrograde direction and a shorter year of 224.7 earth days still look quite friendly but as soon as we come to temperature the beautiful picture of Venus some might have changes into a prediction of the apocalypse or hell. With 480 C mean surface temperature - hot enough to melt lead. The atmosphere’s major part consists of  96% CO2.

Not only Venus’ atmosphere is dry. The overall water sources of the planet could fill an planetwide ocean that is just 0.05 m deep whereas Earth’s water sources could fill an 2,000 m deep ocean and even Mars contains more water with 200 m. Only the Moon is drier: 0.00003 m.

Venus has no satellites and no intrinsic magnetic field except for the solar wind rushing by Venus that creates a pseudo-field around the planet.

2.2.2 Atmosphere

A mighty cloud complex covers Venus and  makes it impossible to see the surface with optical devices. Using infrared and ultraviolet waves, however, clouds and surface have been detected.

The atmosphere mostly consist of 96% CO2 , 3.5% N2 and 0.5% of a mixture of nitrogen, water vapor, argon, carbon monoxide, O2 , Hcl and other gases. the only hydrocarbons or carbohydrates present are there in less than

0.1 parts per million. The clouds are a solution of sulfric acid, hydrochloric acid and hydrofluoric acid. No life can exist on Venus and even the few missions that landed on Venus endured the horrible conditions for only a few hours. The hydrogen found in Venus’ sulfric acid gives a hint how much water there must have been on the planet bevor it disappeared without a trace. The hydrogen contains lots of deuterium typical for H2O.

At 70 km altitude the atmosphere is a haze of small particles. The clouds are at 60 km altitude. In lower layers the particle size of sulfric acid increases. Here sulfur dioxide (SO2) is broken down by ultraviolet light and together with water forms sulfric acid. After condensing and settling it is broken down into SO2 and water again in the lower atmospheres. Here the cycle starts again. This means that although it is raining sulfuric acid it never reaches the surface.

At 45 km altitude the atmosphere becomes clear and brightened by the transmitted sunlight from above. The high reflective clouds of Venus are responsible for two phenomena that contradict each other. On the one hand, there is less absorption of sunlight than on Earth, providing lower temperatures than in Canada. On the other hand, the transmitted sunrays cannot escape to space again but are caught in a solar trap. This is comparable to our greenhouse effect but stores energy much better than on Earth due to the thick clouds of CO2 that cover Venus.

The dense atmosphere causes a surface pressure of 90 atmospheres, which is 90 times that of Earth. But the atmosphere is not static at all.

In high altitudes stormes faster than Hurricanes rush around the planet in four earthdays. This means, the clouds are 60 times faster than the rotation of the planet. The high dynamic is provoked by Venus’ low rotation, short distance to the sun and the temperatures. This instabile system is supposed to be held together by volcanic activity. Evidence can be found in the composition of the atmosphere. According to a modell by David H. Grinspoon sulfur dioxide and carbon dioxide are set free by volcanoes.

2.2.3 Surface

Venus’ relief map is primarily dominated by two large plateaus named Ishtar Terra and Aphrodite Terra. Ishtar Terra is as big as Australia and situated in the northern hemisphere of the planet. Aphrodite Terra is at Venus’ equator and comparable in size with Afrika. This highland makes out one third of the whole surface. In wide areas Venus is even. 70% are giant plains that differ only 1 km from the mean surface level. These have supposedly been floated by lava in the past. 20% are valleys deep 2 km maximal. 10% of the surface are highlands.

Another striking feature of the surface are 10,000 volcanoes that may have big influence in the athmospheric composition. Venus missions have found definitely volcanic areas near the equator. Besides the Earth and Jupiter’s satellite Io, Venus is the third planet in our solar system that bears active volcanoes.

These have also carved big wave-like channels into the ground by means of lava. On Mars there are similar systems that have been cut by water. The longest of the Venusian channels top the Nile’s length with 6800 km.

Volcanic activity probably has resurfaced the planet 300 to 500 million years ago. This theory is based on the fact that only 963 impact craters spread all over the planet have been counted on photos by the Magellan - probe in 1990 to 1994. The craters are 280 km in maximum diameter. There have not been discovered any small craters due to the dense atmosphere that burns up all small impact bodies that enter it.

2.2.4 Missions to Venus

Mariner 2

Launch Date: Aug. 27, 1962

Arrival Date: Dec. 14, 1962

End of Mission: Jan. 3, 1963

Overview

As the first spacecraft to fly by (encounter) another planet, Mariner 2 was built as a backup to Mariner 1, which failed shortly after launch to Venus. Mariner 2 passed as close as 34,773 kilometers (about 20,860 miles) from Venus, discovering the planets' slow retrograde rotation (that is, rotating in the opposite direction of its orbit about the Sun). It found the surface of Venus obscured by continuous cloud cover up to an altitude of about 60 kilometers (36 miles), but using an infrared radiometer, detected at the surface a hot, high-pressure atmosphere, consisting primarily of carbon dioxide. It could find no sign of a Venusian magnetic field. Mariner 2 made the first direct observation of the solar wind, which had been predicted to exist. Mariner 2 was last heard from on January 3, 1963, but is assumed to still be in orbit around the Sun.

Aims

Mariner 2's task was to investigate the characteristics of Venus as it flew past the planet at close range. It carried instruments to gather data about the planet's atmosphere, magnetic field, surrounding charged particles, and mass. During its cruise to Venus and after the encounter, the spacecraft also made measurements of the interplanetary medium, including particles, cosmic rays, cosmic dust, and solar wind.

Mariner 5

Launch Date: Jun. 14, 1967
Arrival Date: Oct. 19, 1967

Overview

Mariner 5 was originally built to be the backup for Mariner 4 to Mars, but was never needed for that purpose. Thus, it was refurbished and modified to go to Venus instead. It flew by Venus at a distance of 3,990 kilometers (2,480 miles), and with its more sensitive instruments than aboard Mariner 2, revealed new information about Venus' atmosphere, including its composition of 85-99% carbon dioxide. Mariner 5 also studied the interplanetary space in the vicinity of Venus and furthered the art and science of building and operating interplanetary spacecraft.

Aims

Mariner 5's task was to find out more about Venus' atmosphere by using radio waves and measuring its brightness using ultraviolet light. The spacecraft was also to sample solar particles and magnetic field fluctuations in the vicinity of Venus.

Mariner 10

Launch Date: Nov. 3, 1973
Arrival Date: Feb. 5, 1974
End of mission: Mar. 24, 1975

Overview

Mariner 10 was the first spacecraft to use a gravity assist trajectory, accelerating as it entered the gravitational influence of Venus, then being flung by the planet's gravity onto a slightly different course to reach Mercury. Requiring more course correction than any previous spacecraft, when the thruster fuel ran low, the solar panels were oriented as sails to use the solar wind as a means of locomotion to assist with course corrections. It was also the first spacecraft to encounter two planets at close range and the first spacecraft to use the new, experimental X-band high-frequency transmitter, allowing faster data transmission to Earth. This Mariner flew past Venus to within 5,800 kilometers (3,600 miles).

Aims

The last in the Mariner series of spacecraft to survey the inner planets of the solar system, the objectives of Mariner 10 were to validate the gravity assist trajectory technique, test the experimental X-band transmitter, and measure the atmospheric, surface, and physical characteristics of Venus and Mercury.

Pioneer Venus Orbiter:

Launch date: May 20, 1978
Arrival date: December 4, 1978
Status: Complete

Multiprobe:

Launch date: August 8, 1978
Arrival date: December 9, 1978 (atmospheric entry)
Status: Complete

Overview

The Pioneer Venus mission had two components: an orbiter and a multiprobe. These spacecraft were launched separately, the orbiter arriving at Venus just a few days ahead of the multiprobe. The orbiter carried 17 experiments, including instruments to see through the clouds and map the surface, as well as measure cloud distribution, atmospheric composition, the magnetic field, the solar wind, properties of the ionosphere of Venus, the gravity field, and gamma ray bursts. The multiprobe spacecraft was actually four separate atmospheric probes hitching a ride on a spacecraft bus. The probes separated from the bus 12.9 million kilometers (8 million miles) before arrival at Venus and entered the atmosphere in different regions of the planet at the same time. The probes made measurements of the structure and composition of the atmosphere all the way to the surface. Meanwhile, the probe bus made measurements in the upper atmosphere, and the Orbiter simultaneously made measurements for comparison.

Aims

The Pioneer Venus spacecraft were intended to study the atmosphere and clouds, including the vertical structure; map the surface using radar; and determine the planet's shape and internal density distribution.

Magellan

Launch Date: May. 4, 1989

Arrival Date: Aug. 10, 1990

End of mission: Oct. 12, 1994

Overview:

Magellan was the first planetary spacecraft to be launched from a space shuttle. It orbited Venus in a near polar, elliptical orbit, with a minimum altitude (periapsis) of 243 kilometers (146 miles). It made detailed maps of 98% of the planet's surface using synthetic aperture radar. Magellan revealed no evidence on Venus of plate tectonics, such as operates with such profound effect on Earth. Volcanoes have left their marks on 85% of Venus, with lava plains, lava domes, large shield volcanoes, and extremely long lava channels. The rest of the surface is covered with ranges of deformed mountains. Magellan also made detailed gravity maps of Venus, determining that the gravity field is highly correlated with surface topography.

Aims

Magellan's primary task was to map the surface of Venus in order to determine its topographic characteristics. The mission was designed to reveal Venus' land forms; its tectonics; the erosion, deposition, impact, and chemical processes at work on the surface; and to model the interior of the planet by studying variations in its gravity field.

2.3 Europa

 2.3.1 General Data

Europa is one of the sixteen Jupiter moons and - with a diameter of 3.121 km - the smallest of the four Galilean moons that were discovered in 1610 by Galileo Galilei and Simon Marius.

It orbits Jupiter, the fifth planet of our solar system, in a distance of 670.900 km. Accordingly the distance from the sun varies, the average distance is 780 million km, which leads to a cold mean surface temperature of -145°C.

The Jupiter moon’s interior consists of an iron core, mantled by a silicate layer and a crust of water and ice.  

2.3.2 Atmosphere:

A team of researchers using the Hubble Space Telescope, which is a project based on the cooperation between NASA and ESA, have identified the presence of an atmosphere of molecular oxygen around Europa. It is so tenuous that its surface pressure is barely one hundred billionth that of the Earth.

The atmosphere is generated by the exposion of the icy surface to the sunlight and the impact of dust and charged particles trapped within Jupiter’s intense magnetic field. These processes cause the frozen water on the surface to produce water vapor and gaseous fragments of water molecules.

After their production, the gas molecules undergo a series of chemical reactions that ultimately form molecular oxygen and hydrogen. The relatively lightweight hydrogen gas escapes into space, while the heavier oxygen molecules accumulate to form an atmosphere which may extend 200 km above the surface. The oxygen gas slowly leaks into space and must be replenished continuously.

Scientists also predicted that Europa might have an atmosphere containing gaseous oxygen, but the instruments of the telescope have not confirmed this presumption yet.

2.3.3 Relief:

The fact that Europa has a “lack” of craters and almost no vertical relief seems to give the evidence that this heavenly body is - in relation to others - still very young.

Europa’s surface is characterized by single mountain ridges, that reach a height up to a few hundred meters and run parallel to each other. Also a network of doubled dark and bright lines crisscrosses Europa’s surface. These so-called “triple bands” could probably be a result of global expansion . This inner movement cracked the surface, and the fractures were filled out with water and then froze.

Beneath the 5 km thick crust of water and ice, Europa may have oceans as deep as 50 km or more. It is conceivable that the tidal heating of Jupiter is strong enough to heat up the icy material to maintain this subsurface liquid water storage.Another existing attempt to explain this potential phenomenon is the thesis that the iron core of Europa has not cooled down enough yet. So the center of the satelite heats the ice up and melts it.

These may existing water resources could have favoured the development of life-forms.

But there is no real reason to get too enthusiastic about this detection. It should not be misinterpreted as an evidence for the presence of life, because this Galilean moon is too cold to support life as we know it.

2.3.4 Missions to Europa

Galileo Orbiter & Probe

Launch date: Oct. 18, 1989
Jupiter arrival date: Dec. 7, 1995 (orbiter and probe)
Status: Primary mission complete Dec. 1997; extended mission to complete Dec. 1999
Probe mission is complete.

Overview

Galileo is the first spacecraft to orbit a gas giant planet and the probe, carried to Jupiter on Galileo, is the first spacecraft to directly sample the atmosphere of an outer planet. The probe entered Jupiter's atmosphere and measured temperature, pressure, chemical composition, cloud characteristics, winds, sunlight and energy internal to the planet, and lightning, all during its brief (approximately one-hour) life before it was crushed, melted, and/or vaporized by the pressure and temperature of the atmosphere. The Galileo orbiter has studied the Jupiter atmosphere, the Galilean (the four largest) moons of Jupiter, and the magnetosphere. Among its discoveries in the Jupiter system so far have been an intense radiation belt above Jupiter's cloud tops, helium in about the same concentration as the sun, extensive and rapid resurfacing of the moon Io because of volcanism, and evidence for liquid water oceans under the moon Europa's icy surface. In an extended mission phase, Galileo is further studying Europa, the thunderstorms of Jupiter, and the volcanic activity of Io, approaching Io as close as 300 kilometers (180 miles) at the end of the mission.

In Fall 1999, the Galileo Mission is preparing to enter an exciting phase - its close-up exploration of Jupiter's moon Io. On October 11 (UTC), the spacecraft will have the first of its two close encounters with Io, flying approximately 500 kilometers above the surface, near what may be currently active, spewing geyser-like volcanoes. If all goes well, Galileo will get images of the moon that are almost 100 times better resolution than anything prior (tens of meters per pixel). The second encounter is November 26 (UTC), and will best the resolution of the October images - Galileo will see details as small as a city bus! This will be a true test of the spacecraft's ability to survive the harsh Jovian radiation environment.

Aims

Galileo's primary mission was to study Jupiter's atmosphere, magnetosphere, and the four largest moons for two years (1995-1997). In an extended mission, for two more years (1997-1999) Galileo is studying in further detail and closer range Jupiter's icy moon Europa and its fiery moon Io.

Europa Orbiter

Proposed Launch date: 2003
Arrival at Europa: 2007
Status: Under study

Overview

Recent images of Europa, fourth largest satellite of Jupiter, hint of a thin frozen crust that may hide a liquid ocean beneath the surface. If liquid water exists on Europa, it is possible that there may also be life there, perhaps forming near undersea volcanic vents. In recent years, life has been discovered in extreme environments on Earth, where no one believed life could exist--too dark, too cold, too salty, too acidic . . .. But life on Earth has been discovered at great ocean depths, beyond the penetration of sunlight, thriving on upwelling chemical nutrients from the interior of the planet. As part of NASA's Outer Planets/Solar Probe Project, preliminary development has begun on a mission to send a spacecraft to Europa to measure the thickness of the surface ice and to detect an underlying liquid ocean if it exists.

Aims

Using an instrument called a radar sounder to bounce radio waves through the ice, the Europa Orbiter sciencecraft would be able to detect an ice-water interface, perhaps as little as 1 km below the surface. Other instruments would reveal details of the surface and interior processes. This mission would be a precursor mission to sending "hydrobots" or remote controlled submarines that could melt through the ice and explore the undersea realm.

3.0 Terraforming

3.1 Terraforming in general

The term of terraforming was originally coined by science fiction literature. Later it was adopted by science and became an official English language term. It defines the concept of making a planet habitable or even viable for humans. To terraform means to transform the planets atmosphere, surface, global temperature and pressure.

In the following we shall be concerned with the different approaches for Mars, Venus and the Jupiter satellite Europa.

3.2 Terraforming plans for Mars, Venus and Europa

 3.2.1 Mars

There are several steps to be done to transform a supposed dead and sterile planet into a fertile environment that supports life as we know it from our Earth.

You can distinguish these into three main branches which work together interactively. As a result, the three parts are not different approaches, but they have to be applied together to get a human-friendly environment.

As a consequence, the depicted steps are merely divided from the whole.

1. Heating up the atmosphere

One big role in adding heat to the atmosphere plays the sun. Its energy can be used with the help of solar sail mirrors positioned behind Mars to reflect the passing light on the dark side of Mars. The effect can be increased by lenses focusing the sunlight onto Mars. This would produce burning points on the surface or the polar caps.

A more aggressive approach is to crush asteroids onto the surface or to burn them up in the atmosphere. Using this method, the atmosphere also thickens which is a useful byproduct for further transformation projects and helps to keep the energy on Mars like it is done on Venus and Earth by the greenhouse effect.

Hydrogen bombs detonated on Mars would increase the surface temperature enormously. A softer method is to generate energy by means of windmills spread all over the planet. Due to its complex wind system, Mars is the right candidate for the technique.

Drilling big moholes into Mars’ surface, the interior’s heat can be set free.

2. Changing the composition and density of the athmosphere

As proposed for Venus by Carl Sagan bacteria, lichen and algae could catalyse Mars’ atmosphere and soil to produce oxygen, methane and ammonia. The latter two are powerful greenhouse gases that reflect energy back onto the surface. A production of 1,000 tonnes per hour can cause a temperature rise of 10° C in a few decades.

By collision of asteroids or iceteroids into Mars as mentioned above, the outgassing CO2 and other gases from the regolith would thicken the atmosphere massively.

Another source of CO2 and water are the polar caps. Melting them one could attain enrichment of water vapor in the surface.

The launching of hydrogen bombs as suggested above would also help here if detonation was beneath the surface.

3. Melting ice for liquid water

To grow crops outdoors on Mars you need a higher temperature as well as liquid water. On the planet itsself there already exists enough water for this purpose. The problem is to melt it. Stored in the polar caps and acquifers underneath the surface it has to be set free.

The needed temperature rise is already given by general terraforming attempts. To support the development dark soil could be spread over the polar caps to reduce their albedo. As a consequence of a lower albedo, more sunlight is absorbed to heat up the ice and to melt it.

The most radical method in setting free Mars’ water resources is to break up big acquifers. The water then would suddenly flood the surface and partly evaporate.

Rising temperatures would also melt the permafrost beneath the surface. This could be gained by launching explosives in the ground, too.

3.2.2 Venus

On the grounds of its high surface temperature, Venus has to be transformed in the opposite way than Mars. The main problem of such an aim is to thin atmosphere to stop the runaway greenhouse effect.

The first proponent for terraforming Venus, Carl Sagan, proposed to set a huge amount of aerial algae free in Venus thick atmosphere to catalyse its CO2 into O2 . On Earth there has not been found algae, that can exist in this dry environment, yet. Although these organisms could be engineered, scientists are faced with another problem. To convert one molecule of CO2 you need one molecule of H2O. As you can see in the chapter above, there is enough water on Venus to cover the planet with a 0.05 m layer of it. To get rid of most of Venus’ CO2 you need the same amount of water that would cover the planet with a 200 m deep layer. All this water could not be transported onto Venus without a scaringly 92 million iceteroids, each with a mass of a billion tonnes.

The only option is to block the sunlight with a solar sail similar to the mirror system proposed for Mars by Robert Zubrin. This sail would be positioned between Venus and the Sun one million kilometers from Venus at the point where gravity, sunlight force and heliocentric centrifugal force balance. Hence, it would keep 90 % of the sunlight away from Venus. After 200 years the CO2 would precipitate onto Venus’ surface as dry ice.

3.2.3 Europa

Mainly, the methods that are used to terraform Mars as mentioned above are almost transferable to Europa.  The main stress has to be laid on the melting of the ice crust to produce liquid water.

Due to the water surface you receive by melting the ice crust, the radical methods could effect positively to the structure. Detonating bombs or crushing ateroids on the ice, big amounts of material could be thrown off and the ice mantle would crack in some places.

Leftover floes are candidates to support preliminary stations or towns.

In the run of the terraforming process, temperatures would rise high enough to melt the rest of the ice.

Using this method, the next step is to evaporate the gained water. Parts of this water leaks into space or break up into oxygen and hydrogen by UV-radiation.

To gain a breathable atmosphere, carbon and nitrogen has to be added.The amount of these deposits included in the ice crust is still unknown.

4.0 Conclusion

Comparing the results of our research, we have come to the following conclusion:

In the first place, the efforts to terraform Venus into a viable planet are much too high for our civilization. The massive density of the atmosphere, its composition and the average temperature of 480° C are great barriers to get over. In addition, rough conditions like the wind system on Venus make it nearly impossible to land on Venus.

Secondly, Europa is on the one hand easy to transform into an underwater world, but on the other hand difficult to change into another Earth. The huge amount of water gained by melting the ice would surely cover the whole planet with an ocean many kilometers deep or result in a moist and heavy atmosphere.

In the third place, Mars is the major candidate to be transformed in the next thousand years on the grounds of the manifold similarities between Mars and Earth suggest to thicken the atmosphere and to increase the temperatures. For most of the terraforming techniques the means are already on Mars. Especially the catalysing of the atmosphere by microorganisms needs huge resources of water. In contrast to Venus there is enough water on Mars. Additionally, stations are easily set up and humans can walk around on the surface in space suits, because the temperatures are acceptable and the pressure and gravity are even lower than on Earth.

5.0 References