OSIRIS-REx is a NASA asteroid sample return mission. The spacecraft OSIRIS-REx has traveled to
the near-Earth asteroid Bennu. Near-Earth asteroid means that Bennu's orbit is similar to that of
Earth's. Its orbit gets a little bit closer to the sun than Earth's orbit. It also takes it
a little bit further away than Earth is from the sun. The spacecraft launched in September of 2016.
It arrived in late 2018 and has been in proximity operations around the asteroid ever since.
The sample will be returned to Earth in September of 2023.
We can learn so much from bringing asteroid material back to Earth.
One of the fascinating things about material that's been in space is that it hasn't been
subjected to the same processes that have evolved material on Earth. So if we go out into the field
on Earth and we pick up a rock we can examine that rock, and we can see what that rock
is like now, and we can infer some of the processes that have affected that rock,
but we can't understand what the original source material was that made that rock to begin with.
And if you extend that back to the origin of Earth itself, we have some idea of the pieces
and the materials that made up the Earth when it first formed, but we don't have a
very good understanding of that raw material itself. And Bennu, and asteroids like Bennu,
are examples of material from the very early solar system that haven't been processed nearly as much
as the material in Earth. So by returning a sample from Bennu to Earth, we will have an opportunity
to study in our labs in incredible exquisite detail what the early ingredients of the Earth
were and those ingredients that led to water on Earth and the formation of life on Earth.
One of the things that's so exciting about returning material from Bennu
is we get an opportunity to investigate what the materials of the early solar system were
like. We can collect material from the surface of Earth and we can examine that material,
but that material has been subjected to a lot of time, excuse me, a lot of temperature
over a very long period of time which has processed and changed the original ingredients
that made the early Earth. It's sort of like baking. You can start out with a set of original
ingredients, mix them together and put them in the oven, and when it comes out of the oven you
have a delicious chocolate chip cookie or a delicious piece of banana bread, but you
don't know what the original source ingredients were like. And the same is true with the Earth.
We can see what the Earth is like today, but we don't really know what those ingredients were
like when the Earth was first forming. And by returning material from Bennu, we'll actually
have an opportunity to investigate the original source ingredients that made the early Earth.
There are many challenges associated with collecting material from the surface of an
asteroid. The first is that the surface of an asteroid is a microgravity environment,
and at Bennu in particular, the gravity is ten thousand times less than the gravity of Earth. So
the behavior and the movement of material is very different than what we expect on Earth. Just the
slightest nudge can send something flying compared to not moving at all on the surface of the Earth.
A second challenge associated with collecting a sample from Bennu is that we don't really know
what the surface properties were like when we were designing the mission. For example, is the
material on the surface of Bennu strong or weak, is it soft or hard? We don't know whether or not
there are a lot of large particles or a lot of small particles or a mixture of particle sizes.
And so we had to make some assumptions based on what we've seen on other asteroids and a
previous sample return mission called Hayabusa which was launched and operated by the JAXA
mission which is the Japanese space agency. So, using data from previous missions,
we've made some estimates about what we thought the surface of Bennu might be like. Those provided
some constraints on what we would expect, but it was a challenge to come up with a scenario,
hardware, and operations that allowed us to sample safely and successfully.
TAGSAM was invented as a way to collect material from an asteroid as simply and as quickly as possible. If you have
a complex mechanism with a lot of moving parts, it can be challenging to understand how those parts will
operate in the microgravity regime of an asteroid. So we wanted it to be as simple as possible
and to operate as quickly as possible because the longer you're in contact with the surface, the
more you're subject to the uncertainty associated with the material properties of that surface.
When TAGSAM releases the gas underneath the sampler head, the gas is able to escape into
space through the screens on the outside of TAGSAM but the material cannot. The material is trapped
by that screen, and that's how we capture and collect sample from the surface of Bennu. And this
is an elegant and simple and fast mechanism to collect material from the surface of an asteroid.
The TAG event is where we actually collect the sample from the surface of the asteroid.
And TAG itself is an acronym that stands for "Touch And Go." The spacecraft approaches the
surface of the asteroid at about 10 centimeters per second, much slower than walking speed. It
contacts the surface for anywhere between a few seconds potentially up to as long as 10 seconds.
During that time, the gas fires, it collects the sample,
and then the back-away thrusters move the spacecraft away from the surface. And TAG is
an acronym, obviously, for "Touch And Go," but it also is kind of like the game of tag where
we're literally just contacting the surface of the asteroid for a very brief period to collect the sample.
Once the spacecraft collects the sample from the surface of the asteroid, it backs away to
a safe distance. It then maneuvers the arm and the TAGSAM head into a series of positions to examine
the head to make sure that we've collected the sample that we want to collect. Once we've
confirmed that's the case, we open up the sample return capsule, which is also called the SRC, and
it puts the sampler head inside the SRC. Once the head is safely inside the SRC, the arm separates
from the sampler head, and the SRC closes, and the spacecraft is ready to return to Earth.
The sample will return to Earth in September of 2023. The spacecraft releases the sample return
capsule a few hours before it reaches the Earth. The spacecraft itself safely passes by Earth
while the sample return capsule passes into the atmosphere and will land in Utah. There's
material on the outside of the SRC called thermal protection system, or TPS, and that protects the
sample from the intense heat that it experiences during the passage through Earth's atmosphere.
A parachute will be released to provide a gentle landing at the surface of Earth. The
engineering and science team that's responsible for recovering the capsule will first process it
in the Utah desert and then fly it to the Johnson Space Center where they have a room that was built
particularly for storing the Bennu sample for now and into the future for scientists to investigate.
The most exciting aspect of the OSIRIS-REx mission for me is the opportunity to be involved with one
of the first robotic sample returns from an asteroid. We are turning points of light that
have lived in our telescopes for hundreds of years into small worlds that we can realize
with the data that we've collected - while we're actually at the asteroid. But we are
actually bringing a piece of that asteroid back to Earth in a pristine form. And it will give us an
opportunity to understand the ingredients that led to the formation of Earth in ways that we could
not have imagined prior to this mission. It's just really a tremendously exciting opportunity.