It has truly been the Golden Age of Planetary Exploration these past two decades, which began on July 4, 1996 when Pathfinder bounced on its airbags to a landing on Mars and deployed the Sojourner Rover. Since then, except for Uranus and Neptune, spacecraft have flown to all of the planets, Pluto, Vesta, Ceres, small asteroids, and comets, and many have orbited, landed, and even roved. With so many spacecraft exploring, it can be hard to keep track, but the following is a breakdown of what has been happening, and what is planned in the years ahead in the exploration of the Solar System.
Mercury: MESSENGER ended its successful orbiting mission on April 30, 2015 after orbiting Mercury since March 17, 2011. There are no spacecraft at Mercury at the moment, but that will change with the launch of BepiColombo scheduled for October 2018. This is an expensive, $1.3 billion (US) dual orbiter spacecraft mission developed and built by the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA). It will split into two spacecraft when it arrives at Mercury on December 5, 2025. Considered a flagship mission, it will bristle with sophisticated instruments that will probe and image Mercury in a way that MESSENGER could not. The primary mission will last one Earth year, but it is hoped it can last several years.
Venus: One of the most neglected planets mainly due to its blistering 900ºF surface, Venus will struggle to get any mission in the years ahead, and yet, it may hold clues to the climate change that is happening on Earth. Akatsuki is currently in orbit studying the weather and environment in the wake of ESA’s successful Venus Express orbiter, which lasted from April 2006 until December 2014. Akatsuki was to go into orbit in December 2010, but due to engine problems had to wait until December 2015 to try again. As a result, science may be compromised as it is in a different orbit than desired, but any science from Venus is valuable because NASA, ESA, and Roscomos (Russia) have no immediate plans to return to Venus. Proposals from science teams in the U.S. for various missions keep getting turned down although new plans for a sophisticated orbiter with a high resolution radar mapper or a relatively long lasting lander are being drafted. If either are approved it will not be until well into the next decade that they will fly. Roscosmos has been planning to build and launch Venera D, a new class of the highly-successful Venera landers, for at least a decade. It was to launch in 2018, then 2021, and now probably no sooner than 2025 due mainly to Russia’s economic problems. This is sad because the Soviet-era Venera landers were the only spacecraft that transmitted a few precious images of the surface of Venus, and that was 30-40 years ago.
Mars: This is the planet that will continue to receive the bulk of the attention and missions into the next decade. There are currently six orbiters and two rovers busily exploring Mars. NASA’s Odyssey is the oldest of the fleet as it has been orbiting Mars since October 2001 and is an important communications relay link for the Opportunity and Curiosity rovers. It may last at least another five years. ESA’s Mars Express has been orbiting Mars since Christmas Day 2003, is still doing science and imaging, and may last several more years. NASA’s Mars Reconnaissance Orbiter has been orbiting Mars since March 2006 and is still going strong in spite of occasional software glitches. It has imaged boulders as small as beach balls and found several old landers, wreckage, and the rovers. It has also acted as a communications relay link for the rovers. MAVEN arrived during September 2014 along with India’s Mars Observer Mission (MOM) and both continue to orbit Mars with MAVEN studying the lower atmosphere, but nothing much has been reported from MOM. ESA’s Trace Gas Orbiter (TGO) arrived last October and its mission is just getting under way to search its atmosphere for methane and other trace gases that could be a signature for life on Mars. It will eventually become the newest communications relay link for the rovers thus relieving the other aging orbiters and reducing the risk of losing critical data from the rovers, or any future landers or rovers.
Exploration of the surface is going strong with the rover Opportunity, affectionately called “Oppy”, still roving the plains of Meridiani at Endeavour Crater after 13 years for a mission expected to last only 90 days after it landed on January 25, 2004. Old age is catching up with it as it has arthritis and bouts of memory loss, but what more can anyone expect for a rover that has done a Martian Marathon traveling over 27 miles. Curiosity landed in Gale Crater on August 6, 2012 and is still going strong as it roves past dunes and climbs Mount Sharp. Since it is nuclear powered, it may last longer than Opportunity.
NASA will finally launch InSight on May 5, 2018 after its March 2016 launch was postponed and will land on November 26, 2018 to study the interior of Mars, its heat flow, and try to detect quakes. It will use solar power and hopefully last several years. ESA is planning to launch a rover to Mars in July 2020 that will land in March 2021 as part of its ExoMars program. NASA is developing another Curiosity-class rover scheduled to launch in July 2020 and land on Mars during March 2021. It will be different than Curiosity as it will have the capability to cache surface samples that could be retrieved on a future mission, and will be able to analyze the soil for evidence of life. A sample return mission always seems to be ten years in the future, but it is looking even worse now as nothing is expected until probably 2030, if then. Astronauts walking on Mars may not occur in our lifetime, maybe by 2040, but given the track record of it slipping every year, it will probably end up being the reality of future generations.
Asteroids: Dawn continues to orbit Ceres on its extended mission and will do so to the very end. It is no longer a healthy enough spacecraft to fly anywhere else, so it will continue to gather science and images at Ceres as long as it can. It will continue to orbit for centuries long after it ceases functioning as it is in a stable orbit. Thanks to its ion propulsion Dawn will also be remembered for successfully orbiting and exploring Vesta from July 2011 until September 2012. OSIRIS-Rex is the big mission under way that was launched last September and is on its way to orbit the asteroid, Bennu, during August 2018. The best part is that it will land on Bennu during July 2019, collect up to four pounds of soil, and return to Earth by September 2023. Psyche is a mission that was just approved and will orbit a metallic asteroid of the same name. It is planned for launch in October 2023 with arrival at Pysche in 2030. Lucy is another asteroid mission that was just approved that will fly from 2025-2033 past a Main Belt asteroid, and several Trojan and Greek asteroids that share the same orbit with Jupiter. Launch is scheduled for October 2021.
Mars may be getting most of the attention, but what about the outer planets? Will we finally sail the murky seas of Titan? Will we finally return to Uranus and Neptune with orbiters? Will Pluto be visited by another spacecraft?