Where did Earth’s water come from? Comets may have brought some of it. Asteroids may have brought some. Icy planetesimals may have played a role by crashing into the young Earth and depositing their water. Hydrogen from inside the Earth may have contributed, too. Another hypothesis states the collision that formed the Moon gave Earth its water.
There’s evidence to back up all of these hypotheses.
But new research suggests that the Sun and its Solar Wind may have helped delivered some water, too.
Right now, the Japanese Aerospace Exploration Agency‘s (JAXA) Hayabusa2 spacecraft is busy exploring the asteroid 162173 Ryugu. Like it’s predecessor, this consists of a sample-return mission, where regolith from the asteroid’s surface will be brought back home for analysis. In addition to telling us more about the early Solar System, these studies are expected to shed light on the origin of Earth’s water (and maybe even life).
Meanwhile, scientists here at home have been busy examining the samples returned from 25143 Itokawa by the Hayabusa1spacecraft. Thanks to a recent study by a pair of cosmochemists from Arizona State University (ASU), it is now known that this asteroid contained abundant amounts of water. From this, the team estimates that up to half the water on Earth could have come from asteroid and comet impacts billions of years ago.
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.
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.
On June 8, the 370-meter (about 1,300-ft.) asteroid 2014 HQ124 breezed by Earth at a distance of just 800,000 miles (1.3 million km). Only hours after closest approach, astronomers used a pair of radio telescopes to produce some of the most detailed images of a near-Earth asteroid ever obtained. They reveal a peanut-shaped world called a ‘contact binary’, an asteroid comprised of two smaller bodies touching.
About one in six asteroids in the near-Earth population has this type of elongated or “peanut” shape. It’s thought that contact binaries form when two or more asteroids get close enough to touch and ‘stick’ together through their mutual gravitational attraction. Asteroid 25143 Itokawa, visited and sampled by the Japanese spacecraft Hayabusa in 2005, is another member of this shapely group.
Radar observations of asteroid 2014 HQ124 seen here in video
The 21 radar images were taken over a span of four hours and reveal a rotation rate of about 20 hours. They also show features as small as about 12 feet (3.75 meters) wide. This is the highest resolution currently possible using scientific radar antennas to produce images. Such sharp views were made possible for this asteroid by linking together two giant radio telescopes to enhance their capabilities.
Astronomers used the 230-foot (70-meter) Deep Space Network antenna at Goldstone, Calif. to beam radar signals at the asteroid which reflected them back to the much larger 1000-foot (305-meter) Arecibo dish in Puerto Rico. The technique greatly increases the amount of detail visible in radar images.
Arecibo Observatory and Goldstone radar facilities are unique for their ability to resolve features on asteroids, while most optical telescopes on the ground would see these cosmic neighbors simply as unresolved points of light. The radar images reveal a host of interesting features, including a large depression on the larger lobe as well as two blocky, sharp-edged features at the bottom on the radar echo (crater wall?) and a small protrusion along its long side that looks like a mountain. Scientists suspect that some of the bright features visible in multiple frames could be surface boulders.
“These radar observations show that the asteroid is a beauty, not a beast”, said Alessondra Springmann, a data analyst at Arecibo Observatory.
The first five images in the sequence (top row in the montage) represent the data collected by Arecibo, and demonstrate that these data are 30 times brighter than what Goldstone can produce observing on its own. There’s a gap of about 35 minutes between the first and second rows in the montage, representing the time needed to switch from receiving at Arecibo to receiving at the smaller Goldstone station.
If you relish up-close images of asteroids as much as I do, check out NASA’s Asteroid Radar Research site for more photos and information on how radar pictures are made.
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.
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.
No news yet if there are specks of asteroid dust in the Haybusa sample return container. JAXA has decided to postpone releasing any information, including publishing a detailed analysis of the particles that may have been collected. According to The Japan Times, JAXA said it is taking more time than originally expected to collect the particles because they are smaller than it was assumed they’d be. This provides some hope, however, that there is actually something of interest in the container.
Originally, JAXA had hoped to publish a report by September, but now it’s looking like December or later.
JAXA said it is going to take several hours to collect just one particle, which likely measures just a few thousandths of a millimeter in diameter. Munetaka Ueno, a senior JAXA official, said the agency wants to analyze the particles with extreme care because repeating the process will be difficult.
The original plan was for JAXA to remove the particles and then let researchers across the country for a more detailed analysis.
We waited seven years for Haybusa to fly to and then return home from asteroid Itokawa, so we should be able to wait a couple more months. Here’s hoping the particle extraction doesn’t encounter as many problems as the spacecraft had.