Detailed view of the rubble-pile asteroid 25143 Itokawa visited by the Japanese spacecraft Hayabusa in 2005. Credit: JAXA
The asteroids in our Solar System are survivors. They’ve withstood billions of years of collisions. The surviving asteroids are divided into two groups: monolithic asteroids, which are intact chunks of planetesimals, and rubble piles, which are made of up fragments of shattered primordial asteroids.
It turns out there are far more rubble pile asteroids than we thought, and that raises the difficulty of protecting Earth from asteroid strikes.
Let’s not sugarcoat it. Exploring the Moon is not for the faint of heart! It’s an airless body, which means there is no atmosphere, the surface temperatures are extreme, and there’s lots of radiation. The low gravity also means you can never really walk on the surface and have to bounce around in a bulky spacesuit until you fall over. And you can bet your bottom dollar people will make a supercut of the footage someday (see below). Then there’s that awful moondust (aka. lunar regolith), which is electrostatically charged and sticks to EVERYTHING!
Looking to take advantage of this, researchers from the Massachusetts Institute of Technology (MIT) began testing a new concept for a hovering rover that harnesses the Moon’s natural charge to levitate across the surface. On the Moon, this surface charge is strong enough to levitate moon dust more than 1 meter (3.3 ft) above the surface. With support from NASA, this research could lead to a new type of robotic exploration vehicle that will help astronauts explore the Moon in the coming years.
Panspermia is an idea that has been around for a long time. It was first mentioned in the 5th century BC by Anaxagoras, one of the most prominent pre-Socratic philosophers. The problem with the theory is that there’s never really been any evidence to back it up. That lack of evidence has changed dramatically in the last 20 or so years, and recently more data has been added to that dataset. A team from Royal Holloway, part of the University of London, found organic material and water in a sample of Itokawa, the asteroid the first Hayabusa mission visited over 10 years ago.
Hayabusa 2 has collected a sub-surface sample from asteroid Ryugu. Image: JAXA
Japan’s Hayabusa 2 spacecraft is now the first spacecraft to retrieve a subsurface sample from an asteroid. On July 11th, the spacecraft touched down for a second time on asteroid 162173 Ryugu. This time, the probe retrieved a sample from a crater it excavated with its impactor.
The cross section area of the particle collected from the asteroid Itokawa using Hayabusa spacecraft. Credit: Osaka University
Within Earth’s orbit, there are an estimated eighteen-thousands Near-Earth Asteroids (NEAs), objects whose orbit periodically takes them close to Earth. Because these asteroids sometimes make close flybys to Earth – and have collided with Earth in the past – they are naturally seen as a potential hazard. For this reason, scientists are dedicated to tracking NEAs, as well as studying their origin and evolution.
The surface patterns on one of the microscopic dust particles from asteroid Itokawa. Image: JAXA
In 2003, the Japanese Aerospace Exploration Agency (JAXA) launched the Hayabusa probe. Its mission was to rendezvous with asteroid 25143 Itokawa in 2005. Once there, it studied a number of things about Itokawa, including its shape, topography, composition, colour, spin, density, and history. But the most exciting part of its mission was to collect samples from the asteroid and return them to Earth.
The mission suffered some complications, including the failure of Minerva, Hayabusa’s detachable mini-lander. But Hayabusa did land on the asteroid, and it did collect some samples; tiny grains of material from the surface of Itokawa. This was the first time a mission had landed somewhere and returned samples, other than missions to the Moon.
The Hayabusa spacecraft burned up on re-entry into Earth’s atmosphere, but the capsule containing the samples survived. The glowing piece on the bottom front of the debris stream is the sample capsule. Image: NASA Ames, Public Domain
Once the collected grains made it back to Earth in 2010, and were confirmed to be from the asteroid, scientists got excited. These grains would be key to helping understand the early Solar System when the planetary bodies were formed. And they have revealed a sometimes violent history going back 4.5 billion years.
The grains themselves are truly microscopic, at just over 10 micrometers in size. The marks and surface patterns on them are measured in nanometers. Initially, all the marks on the surfaces of the particles were thought to be of one type. But the team behind the study used electron microscopes and X-Ray Microtomography to reveal four different types of patterns on their surfaces.
One 4.5 billion year old pattern shows crystallization from intense heat. At this time period, Itokawa was part of a larger asteroid. The second pattern indicates a collision with a meteor about 1.3 billion years ago. Another pattern was formed by exposure to the solar wind between 1 million and 1,000 years ago. A fourth pattern detected by scientists shows that the particles have been rubbing against each other.
The team has concluded that Itokawa didn’t always exist in its current shape and form. When it was formed over 4 billion years ago, it was about 40 times bigger than it is now. That parent body was destroyed, and the researchers think that Itokawa re-formed from fragments of the parent body.
If there is still any lingering doubt about the violent nature of the Solar System’s history, the grains from Itokawa help dispel it. Collision, fragmentation, bombardments, and of course solar wind, seem to be the norm in our Solar System’s history.
The return of these samples was a bit of a happy accident. The sample collection mechanism on Hayabusa suffered a failure, and the returned dust grains were actually kicked up by the landing of the probe, and some ended up in the sample capsule.
For their part, JAXA has already launched Hayabusa’s successor, Hayabusa 2. It was launched in December 2014, and is headed for asteroid 162173 Ryugu. It should reach its destination in July 2018, and spend a year and a half there. Hayabusa 2 is also designed to collect asteroid samples and return them to Earth, this time using an explosive device to dig into the asteroid’s surface for a sample. Hayabusa 2 should return to Earth in December 2020.
An artist’s image of Hayabusa leaving Earth. Image credit: JAXA
Hayabusa suffered several failures, including the failure of its mini-lander, problems with sample collection, and it even suffered damaged to its solar panels caused by a solar flare, which reduced its power and delayed its arrival at Itokawa. Yet it still ended up being a success in the end.
If Hayabusa 2 can avoid some of these problems, who knows what we may learn from more intentional samples. Sample missions are tricky and complex. If Hayabusa can return samples, it would be only the fourth body to have samples successfully returned to Earth, including the Moon, asteroid Itokawa, and comet Wild 2.
As of November 2014, these are all of the planetary, lunar and small body surfaces where humanity has either lived, visited, or sent probes to. Composition by Mike Malaska, updated by Michiel Straathof. Image credits: Comet 67P/C-G [Rosetta/Philae]: ESA / Rosetta / Philae / CIVA / Michiel Straathof. Asteroid Itokawa [Hayabusa]: ISAS / JAXA / Gordan Ugarkovic. Moon [Apollo 17]: NASA. Venus [Venera 14]: IKI / Don Mitchell / Ted Stryk / Mike Malaska. Mars [Mars Exploration Rover Spirit]: NASA / JPL / Cornell / Mike Malaska. Titan [Cassini-Huygens]: ESA / NASA / JPL / University of Arizona. Earth: Mike Malaska
Correction, 11:33 a.m. EST: The University of Central Florida’s Phil Metzger points out that the image composition leaves out Eros, which NEAR Shoemaker landed on in 2001. This article has been corrected to reflect that and to clarify that the surfaces pictured were from “soft” landings.
And now there are eight. With Philae’s incredible landing on a comet earlier this week, humans have now done soft landings on eight solar system bodies. And that’s just in the first 57 years of space exploration. How far do you think we’ll reach in the next six decades? Let us know in the comments … if you dare.
More seriously, this amazing composition comes courtesy of two people who generously compiled images from the following missions: Rosetta/Philae (European Space Agency), Hayabusa (Japan Aerospace Exploration Agency), Apollo 17 (NASA), Venera 14 (Soviet Union), the Spirit rover (NASA) and Cassini-Huygens (NASA/ESA). Omitted is NEAR Shoemaker, which landed on Eros in 2001.
Before Philae touched down on Comet 67P/Churyumov–Gerasimenko Wednesday, the NASA Jet Propulsion Laboratory’s Mike Malaska created a cool infographic of nearly every place we’ve lived or visited before then. This week, Michiel Straathof updated the infographic to include 67P (and generously gave us permission to use it.)
And remember that these are just the SURFACES of solar system bodies that we have visited. If you include all of the places that we have flown by or taken pictures from of a distance in space, the count numbers in the dozens — especially when considering prolific imagers such as Voyager 1 and Voyager 2, which flew by multiple planets and moons.
To check out a small sampling of pictures, visit this NASA website that shows some of the best shots we’ve taken in space.
Watch out, asteroid 1999 JU3: you’re being targeted. As severalmediareports reminded us, the Japan Aerospace Exploration Agency (JAXA)’s Hayabusa-2 asteroid exploration mission will carry a ‘space cannon’ on board — media-speak for the “collision device” that will create an artificial crater on the asteroid’s surface.
“An artificial crater that can be created by the device is expected to be a small one with a few meters in diameter, but still, by acquiring samples from the surface that is exposed by a collision, we can get fresh samples that are less weathered by the space environment or heat,” JAXA states on its website.
Reports indicate JAXA is on schedule to, er, shoot this thing into space for a 2018 rendezvous with an asteroid. The spacecraft will stick around the asteroid for about a year before heading back to Earth in 2020. The overall aim is to learn more about the origin of the solar system by looking at a C-type asteroid, considered to be a “primordial body” that gives us clues as to the early solar system’s makeup.
Artist's conception of Hayabua 2 approaching the asteroid 1999 JU3. Credit: Akihiro Ikeshita/JAXA
[/caption]
In 2010, the Japanese spacecraft Hayabusa completed an exciting although nail-biting mission to the asteroid Itokawa, successfully returning samples to Earth after first reaching the asteroid in 2005; the mission almost failed, with the spacecraft plagued by technical problems. The canister containing the microscopic rock samples made a soft landing in Australia, the first time that samples from an asteroid had been brought back to Earth for study.
Now, the Japanese government has approved a follow-up mission, Hayabusa 2. This time the probe is scheduled to be launched in 2014 and rendezvous with the asteroid known as 1999 JU3 in mid-2018. Samples would again be taken and returned to Earth in late 2020.
1999 JU3 is approximately 914 metres (3,000 feet) in diameter, a little larger than Itokawa, and is roughly spherical in shape, whereas Itokawa was much more oblong.
As is common for any space agency, the Japanese Aerospace Exploration Agency (JAXA) is working with tight budgets and deadlines to make this next mission happen. There is a possibility of a back-up launch window in 2015, but if that deadline is also not met, the mission will have to wait another decade to launch.
The asteroid Itokawa, visited by Hayabusa in 2005. Credit: JAXA
One of the main problems with Hayabusa was the failure of the sampling mechanism during the “landing” (actually more of a brief contact with the surface with the sample capturing device) to retrieve the samples for delivery back to Earth. Only a small amount of material made it into the sample capsule, but which was fortunate and ultimately made the mission a limited success. The microscopic grains were confirmed to have primarily come from Itokawa itself and are still being studied today.
To avoid a repetition of the glitches experienced by Hayabusa, some fundamental changes needed to be made.
This next spacecraft will use an updated ion propulsion engine, the same propulsion system used by Hayabusa, as well as improved guidance and navigation systems, new antennas and a new altitude control system.
For Hayabusa 2’s sample-collecting activities, a slowly descending impactor will be used, detonating upon contact with the surface, instead of the high-speed projectile used by Hayabusa. Perhaps not quite as dramatic, but hopefully more likely to succeed. Like its predecessor, the main objective of the mission is to collect as much surface material as possible for delivery back home.
Hopefully Hayabusa 2 will not be hampered by the same problems as Hayabusa; if JAXA can achieve this, it will be exciting to have samples returned from a second asteroid as well, which can only help to further our understanding of the history and formation of the solar system, and by extrapolation, even other solar systems as well.
