Australian Sky & Telescope - June 2018

34 AUSTRALIANSKY&TELESCOPEJuly 2018 http://www.skyandtelescope.com.au 34

capsule will enter the atmosphere over the Utah Test and

Training Range west of Salt Lake City, Utah, on September 24,

2023, marking the end of Osiris-REX’s primary mission but

the start of a journey of discovery for the global community of

planetary scientists who will dig in to the gritty treasure.

Pushing back the frontiers

The samples returned from both of these groundbreaking

missions and the new knowledge gained about their parent

asteroids will not only finally tell us how the different

flavours of carbonaceous chondrite meteorites are related to

various types of dark asteroids. They’ll also provide crucial

steps forward in planetary science and exploration.

One of the most fundamental questions we have about the

formation of our own home world is: Where did Earth’s water

and organic materials come from? Were they present in the

material Earth itself formed from, or were they delivered to

Earth after the planet was assembled?

For many years, scientists’ favored answer was that Earth’s

water came from comets that had hit the planet early on,

but as we’ve studied comets’ compositions we’ve realised

that the isotopes in their water don’t match Earth’s. Instead,

our planet’s water might be ‘native,’ carried in the rocks

that stuck together to build our world up — the same rocks

that endure today as asteroids. Finally getting our hands on

samples plucked from the types of asteroids long suspected

to be the most primitive building blocks of the terrestrial

planets will go a long way to answering these questions.

In addition to their compelling scientific value, the

near-Earth asteroids are literally gold mines in the sky: Not

only do we think they contain precious metals, they also

should have water that we can convert into spacecraft fuel,

providing important in situ resources once we’re routinely

exploring and navigating the inner Solar System.

Just operating in close proximity to Ryugu and Bennu is

going to provide crucial knowledge that will come in hand

as we expand our experience working in space beyond Ea

Hayabusa 2 and Osiris-REX are pioneers in helping us wr

our heads around the sometimes counterintuitive workin

environments we’re going to encounter on the surfaces o

these lumpy little worlds.

And of course, there’s always the looming problem of

to do if an asteroid targets Earth. Although a civilisation

ending hit is unlikely, smaller rocks could come. An aster

impact is a natural disaster that we can actually prevent,

but only if we know more about the asteroids themselves

and how they respond to our poking and prodding. So as

exaggerated as it sounds, these missions might not

only tell us about Earth’s past — they could also help

us preserve its future.

„ DAN DURDA is a principal scientist at the Southwest

Research Institute, where he studies the evolution of aster

and the effects of their impacts on one another and on Ea

TNASA’S STRATEGY Expecting a rubble-strewn surface, Osiris-

REX will forego projectiles when it touches down on Bennu (1). Once

its sampling head is securely planted on the asteroid’s surface, it

will release a burst of nitrogen gas (2), kicking up dust and small

pebbles into the instrument. A few seconds after touchdown, the

spacecraft will lift off (3), stowing the sample in its return capsule on

the craft’s underbelly (4).

12

34

OSIRIS-REX: NASA; SAMPLING: GREGG DINDERMAN /

S&T

ndy

arth.

rap

ng

of

what

• roid

roids

rth.

TOSIRIS-REX

INSTRUMENTS

X-ray imaging

spectrometer

Laser altimeter

Camera

suite

Thermal

emission

spectrometer

Visible and IR

spectrometer

ASTEROID PLUNDERING