21st Century Exploration So Far

Other Inner Planets

The inner solar system, composed of Mercury, Venus, and Mars (besides Earth), has generally presented an easier target for study than the far-off outer planets. Within the last ten years, Mars, especially, has been the most intriguing target for study. So far this century has only seen missions to Mars, both by NASA and the ESA. These include 2001 Mars Odyssey, Mars Express, and Mars Exploration Rovers. Additionally, the MESSENGER craft to Mercury has been launched, but it won't reach the planet until 2011; the Mars Reconnaissance Orbiter was also launched, and it will reach Mars in 2006.

The 2001 Mars Odyssey was originally called the Mars Surveyor 2001 Project, and was to consist of both a lander and an orbiter. However, due to cut-backs and reorganization, the lander was abandoned and the orbiter set as the only part of the project.

The orbiter is designed to orbit Mars for over five years and to collect data for three of those. The probe is designed to take measurements on Mars' mineral content and atmosphere / environment. One of the main objectives for this project is to attempt to determine if Mars ever had a suitable environment for life to develop. Other objectives are to learn about the climate and geology of Mars, as well as to determine any potential radiation hazards to potential astronaut visitors.

2001 Mars Odyssey was launched on April 7, 2001. After seven months, it reached Mars on October 23, 2001. Over the next three months, it used the Martian atmosphere to aerobrake, and to finally assume a standard orbit on January 30, 2002, of approximately 400 km (250 mile) altitude. It orbits the planet now every two hours.

Besides its primary science objectives, the 2001 Mars Odyssey will also be used as a relay station for rovers that will be sent to Mars later this year (2003), and possibly other probes as well. Even though its 917-day mission ended in July of 2004, NASA extended the mission an additional Martian year through September 2006. Afterwards, if the craft is still working, NASA plans on continuing to use the probe as a relay station for communications with other probes in orbit and on the surface.

This consists of an orbiter, Mars Express Orbiter, and a lander, Beagle 2. The purpose of the orbiter is to take global high-resolution photography (10 m (33 foot) resolution), mineralogical mapping (100 m (330 foot) resolution) and mapping of the atmospheric composition, study the subsurface structure, global atmospheric circulation, interaction between the atmosphere and the subsurface, and the atmosphere and interplanetary composition. The Beagle 2 lander is supposed to characterize the landing site geology, mineralogy, and geochemistry, the physical properties of the atmosphere and surface layers, collect data on the meteorology and climatology, and to search for possible signatures of life.

The craft was launched on June 2, 2003. It reached Mars on December 26, 2003, but the lander was released on December 21, 2003. The orbiter entered into a highly elliptical orbit, which, after a few days, was altered into a polar orbit that will eventually settle into a 250x11,583 km (155x7200 mile) orbit at 86° of 6.7 hours. This will begin the main mission, and it will last approximately 440 days. Then, the orbit will be modified so that the farthest point will be at 10,243 km (6365 miles) above the surface. The total orbiter mission is planned to last one Martian year - approximately 687 days.

The Mars Express radar system (MARSIS) was deployed between May 2 and June 19, 2005. It was commissioned over the next few weeks, and it began its first science observations in August 2005.

The Beagle 2 entered the atmosphere on December 26, 2003, and released parachutes when it was approximately 1 km (0.62 miles) above the surface. The Beagle 2 lander was declared lost on February 6, 2004, after it had not contacted any orbiting craft nor receiver on Earth.

What was supposed to happen was large gas bags were to inflate around the lander to protect it when it hit the surface. After landing, the bags would deflate and the top of the lander will open to expose four solar array disks. Within the body of the lander, an antenna would have been deployed and the lander arm released. The lander arm would have dug up samples to be deposited in the various instruments for study; the "mole" was to be deployed, crawling across the surface at a rate of about 10 cm (4 inches) per minute and capable of burrowing under rocks to collect soil samples for a gas analysis system.

This program is another that plans on landing on Mars. It is designed to take panoramic pictures, search for evidence of past or present water, and perform other experiments on rocks. Scientists from Earth will be able to command the vehicles to specific areas of interest.

It consists of two rovers that are based upon that used in the Mars Pathfinder mission. The first was launched on June 10, 2003, and it landed on January 3, 2004 (GMT). The second rover was launched on July 7, 2003, at 23:18:15 EDT, and it landed on January 25, 2004 (GMT).

The rovers are designed to travel approximately 100 m (330 feet) each martian day (24 hours and 37 minutes). Each rover's primary mission lasted for approximately 90 Martian (92 Earth) days. However, they have been successfully operating for nearly a full Martian year, and they have had their missions extended until at least November, 2006, assuming they continue to operate. For more up-to-date information, see the Current Events, and for information on what the craft have discovered, see the Mars page.

This mission owes its existence to the ESA Mars Express mission. The ESA wanted to reuse the design of Mars Express as well as have it ready to launch in 2005. Out of all the proposals, Venus Express was chosen in 2002 because it would make use of the spare instruments developed for Mars Express and Rosetta to achieve the main science objectives - studying the atmosphere in detail.

This will be the ESA's first mission to Venus, with the USA and Russia being the only two countries / space programs to have sent craft to Venus. This probe will be the first craft to perform a global investigation of the Venusian atmosphere. It will also be the first craft to study Venus' surface using the recently discovered "visibility windows" in the infrared part of the spectrum.

Venus Express was launched on a Soyuz-Fregat launcher from Baikonur Cosmodrome in Kazakhstan on Wednesday, October 26, 2005, at 06:33 CEST (04:33 GMT, 10:33 local time). Its journey to Venus will last 153 days, when it will be captured by Venus' gravity in April 2006, and take five days to achieve its planned elliptical orbit of 250x66,000 km (155x41,000 miles). The mapping mission should last for about two Venus days (~500 Earth days), and it may be extended depending upon the craft's health.

Though the craft is used from many of the spare components of Mars Express, Venusian environmental conditions are very different to those encountered around Mars. Solar flux is four times higher and it has been necessary to adapt the spacecraft design to this hotter environment, notably by entirely redesigning the thermal insulation. Whereas Mars Express sought to retain heat to enable its electronics to function properly, Venus Express will in contrast be aiming for maximum heat dissipation in order to stay cool.

To accomplish its science studies, it has seven instruments onboard: Three are flight-spare units of instruments already flown on Mars Express, two are from comet-chaser Rosetta and two were designed specifically for this mission.

MESSENGER No craft has visited Mercury since Mariner 10 in 1975. Since then, many questions about Mercury have been raised, and it is hoped that this mission will answer some of them. This mission is designed to study the characteristics and environment of Mercury from orbit. Specifically, the objectives are to study the surface composition, geologic history, core and mantle, magnetic field, tenuous atmosphere, and to search for water ice and other frozen volatiles at the poles over a nominal orbital mission of one Earth year (365 days).

The craft was launched on August 3, 2004, at 6:15:56 UT (2:15:56 A.M. EDT) on a Delta 7925H (a Delta II Heavy launch vehicle with nine strap-on solid-rocket boosters). The spacecraft was injected into solar orbit 57 minutes later. The solar panels were then deployed and the spacecraft began sending data on its status. One year after launch, on August 2,2005, MESSENGER flew by Earth at an altitude of 2347 km. On December 12, 2005, at 11:30 UT, MESSENGER fired its large thruster for 524 seconds, changing the spacecraft velocity by 316 m/s and putting it on course for its October 24, 2006, Venus flyby at an altitude of 3612 km. There will be another Venus flyby on June 6, 2007, at an altitude of 300 km.

The first of three Mercury flybys, all at 200 km altitude, will be on January 15, 2008, the second will be on October 6, 2008, and the third on September 30, 2009. There will also be five deep space maneuvers. Data collected during the Mercury flybys will be used to help plan the scientific campaign during the orbital phase. Mercury orbit insertion will take place on March 18, 2011, requiring a change in velocity of 0.867 km/s.

The nominal orbit is planned to have a periapsis of 200 km at 60° N latitude, an apoapsis of 15,193 km, a period of 12 hours and an inclination of 80°. The periapsis will slowly rise due to solar perturbations to over 400 km at the end of 88 days (one Mercury year) at which point it will be readjusted to a 200 km, 12 hour orbit via a two burn sequence. Data will be collected from orbit for one Earth year, and the nominal end of the primary mission will be in March 2012.

Global stereo image coverage at 250 m/px resolution is expected. The mission should also yield global composition maps, a 3-D model of Mercury's magnetosphere, topographic profiles of the northern hemisphere, gravity field to degree and order 16, altitude profiles of elemental species, and a characterization of the volatiles in permanently shadowed craters at the poles.

Mars Reconnaissance Orbiter This mission, called MRO for short, is an orbiter to study the martian surface. The primary objectives are to study the weather and climate of Mars and to help identify landing sites for future missions. Besides a visual imager with a resolution better than one meter (three feet), the orbiter will carry a spectrometer to analyze the surface composition. Provided by the Italian Space Agency, a shallow subsurface sounding radar (SHARAD) will be included to search for underground water. The orbiter will also be closely tracked to give information on the gravity of Mars.

MRO was launched on August 12, 2005, at 11:43 UT (7:43 A.M. EDT) from the Kennedy Space Center. It fired its main rockets on August 30, 2005, for a main course correction, and the rockets will not be used again until it reaches Mars. It will reach Mars on March 10, 2006, and it will spend six months aerobraking to reach an eventual polar orbit of 255x320 km (160x200 miles). The planned science mission will last approximately one martian year (687 days), from November 2006 through November 2008.

After it's main mission, the orbiter will serve as a communications relay for future missions. This will be the first part of an "interplanetary internet" to be used for communications back and forth between Earth and Mars to be used by international spacecraft. The mission will also test an experimental optical navigation camera that will serve as a high-precision interplanetary "lighthouse" to guide incoming spacecraft nearing Mars.