July 20, 1976, will be forever remembered by space enthusiasts. On that day, Viking 1 became the first U.S. spacecraft to land on another planet – in this case, Mars (the USSR Venera 9 spacecraft landed on Venus in 1975). That lander, and Viking 2 which followed it Sept. 3, 1976, paved the way for more complex missions later on, which would begin to finally unlock some of the secrets of the mysterious Red Planet. The two Viking landers, and their counterpart orbiters, were genuine trailblazers, opening up the vast Martian landscape to robotic and human eyes for the first time.
The Solar System is a busy place, with spacecraft currently visiting most of the planets as well as some dwarf planets and comets. Akatsuki is at Venus, several rovers and orbiters are at Mars, the Juno spacecraft just reached Jupiter, Cassini is still orbiting Saturn, Dawn is still at Ceres, and Rosetta continues to study the comet 67P. Mercury, Uranus, Neptune, and Pluto have all been visited by previous missions as well. But there is one other place in the Solar System which will also be explored more closely in the near future: the Sun.
Over the past couple decades, astronomers have been discovering a seemingly endless variety of exoplanets orbiting other stars. Some are rather similar to planets in our own Solar System, while others are more like ones depicted in science fiction, ranging from rocky worlds about the size of Earth and larger, to massive, searing hot planets larger than Jupiter orbiting very close to their stars. Tatooine is another well-known example – the desert planet orbiting two suns in the Star Wars films. Now astronomers have found a similar world, using direct imaging, but which orbits within a system of three stars.
Jupiter has often been referred to as the King of Planets, and for good reason, as it is a massive gas giant, much larger than Earth and the largest planet in our Solar System. It is more than 2.5 times as massive as all the other planets combined, and is a mesmerizing world of colourful bands of clouds wrapping around the globe, which can be seen even in a small telescope, but exhibit incredible detail when seen by spacecraft. Jupiter is also itself the center of a sort of miniature solar system, with dozens of moons orbiting around it. We’ve seen this world up close before by spacecraft such as Voyager and Galileo, but now a new visitor has arrived in the Jovian system: NASA’s spacecraft Juno.
So-called “waterworlds” have been found to be surprisingly common in the Solar System – small icy moons which have ice crusts but oceans of liquid water below the surface. These include Jupiter’s moons Europa and Ganymede and Saturn’s moons Enceladus and Titan, and possibly others. These moons are cold and very far from the Sun, but heated inside by the gravitational pull of their giant host planets and/or radioactivity. Now there’s another Solar System body which, even more surprisingly, some scientists think has a subsurface ocean: Pluto.
NASA’s current rovers, Curiosity and Opportunity, are continuing to explore their respective regions of Mars, with new findings that are providing yet more clues as to the geological history and potential past habitability of this fascinating world. They have also both just completed significant steps in their journeys and are now entering new and exciting phases of their missions. Both missions have found yet more evidence that the Mars we see today – cold and dry – was once much wetter and potentially habitable, at least for microorganisms.
Sending human astronauts to Mars is a dream shared by many, but there are still challenges to overcome and the question of just how to accomplish it is a subject of intense debate. Some supporters advocate sending a mission directly to Mars, while others think that returning to the Moon first, for potentially beneficial training, is the way to go. Indeed, former astronaut James Lovell, who flew on two trips to the Moon, has also called for a return to the Moon first. NASA itself has stated its desire to send a crewed mission to a nearby asteroid first, instead of the Moon, going a bit farther into space than the Moon as its idea of preparation for the much longer journey to Mars. A major problem has been that NASA has still not set a firm timetable for such a mission; it wants to go to Mars, but the steps to achieving that goal are still unclear.
The New Horizons mission to Pluto has been nothing less than incredible, giving us our first close-up views of this enigmatic dwarf planet and its moons. But the show isn’t over yet, as the New Horizons team is now planning for its next encounter with another Kuiper Belt Object (KBO) in 2019. But even before then, the spacecraft has been busy observing other smaller objects, and has now collected the first science data on one of them, called 1994 JR1.
For several years now the Kepler Space Telescope, as well as other telescopes, has been discovering an increasing number of exoplanets, with over 2,000 such confirmed worlds found so far (and nearly 5,000 candidates). Today, NASA announced that the Kepler mission has added 1,284 newly confirmed exoplanets to that list, vastly increasing the number of known planets orbiting other stars. This is the largest number of new planets ever announced at one time. The new results were announced during a NASA teleconference briefing.
Mars’ atmosphere is thin and cold, composed primarily of carbon dioxide along with other trace gases and some water vapour. Evidence has continued to mount, however, that the rarified atmosphere we see today once used to be much thicker and possibly warmer, making it potentially more life-friendly early on. Just how thick and how warm is still a subject of much debate, but there is also another interesting aspect to all of this: New evidence from the Curiosity rover has shown that the Martian atmosphere also used to have a lot more oxygen in it than it does now. Today, only very small traces of oxygen can be found, as opposed to Earth’s oxygen-rich atmosphere. So what does this mean? Could there be biological implications?