In about 4 days, a mission that was started
on 5 May 2018 will reach its critical phase. On 26 November 2018, NASA’s newest
Mars probe is set to enter the Martian atmosphere, and begin its ‘seven minutes
of terror’, as it enters the atmospheric entry, descent and landing phase of
the mission. For it to successfully land on Mars, it needs to hit the
atmosphere at the exact right angle.
During these seven minutes, the InSight
probe will be travelling at almost 21 000 km/h as it enters the atmosphere.
Its heat shield will increase in temperature to about 1 370 degrees
Celsius, as the friction with the atmosphere brakes the spacecraft. After about
3 to 5 minutes, when it has slowed enough for the parachute to deploy. Thirty
seconds after deployment, the heat shield will be jettisoned, and the onboard
radar will be activated. This allows the craft to measure its speed and height
above Mars.
Then, 40 seconds before touchdown, it will
jettison the parachute as well, and start freefalling, spinning away from the
parachute and heat shield. Finally, just before it hits the ground, it will
fire its rocket thrusters in preparation for contact and slow its speed. In
those seven minutes, it would have reduced its speed from 21 000 km/h to
just 8km/h as it lands on the planet, and thus successfully increasing the
active robot population on Mars to two.
Landing on Mars is hard, as only 40% of all
missions sent to the red planet have been successful. All of these have been by
NASA, and their recent missions have been quite successful. After the first
Sojourner rover lasted just under three months on Mars’ surface, the next few
far exceeded their operational lifetimes. In particular, the Spirit rover was
planned to be operational for only 90 Martian solar days but lasted 2 269
days until contact was lost on 22 March 2010, while the Opportunity rover
mission was also planned for 90 Martian solar days, and lasted 5 613 days
before entering hibernation after a dust storm on 10 June 2018.
As such, the Curiosity rover was designed
for an operational lifetime of 668 Martian solar days and is currently on day
2237 of its mission – currently the only robot active on Mars. InSight,
however, is something different, as its mission is not to explore the surface
of Mars, but rather the interior of Mars. Its name is a backronym for INterior
exploration using Seismic Investigations, Geodesy and Heat Transport (INSIGHT)
which describes the instruments this Mars lander carries.
Insight will take measurements of the
inside of Mars, via seismology, heat flow and radio science. Why? Well, to tell
us more about how planets were formed. While we’ve had ample opportunity to
study our own planet, we’ve had no readings of the interior of other planets to
compare it to. Mars and Earth seem like they were close to identical at one
point in the past – about 3 to 4 billion years ago. Both were warm, humid, and
covered in thick atmospheres. But in the time since then, these two took
different paths.
Essentially, this mission is trying to
examine why Mars essentially stopped changing, while the Earth never stopped.
The Earth developed tectonic plates that converge across the surface of the
planet and allow new crust to emerge from the inside of the planet. This new
crust brings along more than rock – it releases some gases which are vital to
life, such as water, carbon dioxide and methane. Mars, however, does not seem
to have tectonic plates, and InSight seeks to try and measure marsquakes for
the first time to try and study its interior. Each marsquake will set off
seismic waves that can be studied to illuminate the structure of Mars for the
first time.
Rocky planets also trap heat in their
interior, either at formation, or via radioactive decay of elements over time.
This heat could have been responsible for Mars’ early conditions, and its
evolution into the red planet we know now. For this reason, InSight also
contains a heat probe that will be drilled 5 meters into the planet, to try and
discover how this heat shaped the planet.
Heat also keeps a planet’s core molten, and
as its metallic elements flow, they generate electric currents. On Earth, this
results in a magnetic field around the planet, which not only aided us in
navigating the planet by allowing equipment such as compasses to work, but also
shields the planet from certain types of radiation. Mars, however, had a strong
magnetic field once, but it seems to have dissipated. InSight therefore
contains a radio experiment to detect the wobble of Mars’ axis, and via that,
to learn more about the planet’s core, which in turn provide clues as to why
its magnetic field disappeared.
So with the dreaded ‘seven minutes of
terror’ in sight, hopes are high that this mission will succeed. InSight could
provide much insight not only into the early formation of our own planet, but
also into what features to look for in extrasolar planets that makes them much
more compatible to supporting life. The insights gained from this mission could
dwarf those from prior missions, and we might finally have the first clues to
point us towards extra-terrestrial life in sight.