In the coming week, we will get our closest view of one of the farthest planets of our solar system as NASA’s New Horizons spacecraft whizzes past Pluto.The unmanned New Horizons probe has taken nine years to cover the 7.5 billion kilometer distance from Earth. Still, all we get is a look at the sun-lit face of the dwarf planet and its moon Charon. New Horizons won’t orbit or land on Pluto.

So why is NASA spending some $700 million on this expedition if it can’t touch the ice surface of Pluto? It’s a Catch-22 situation arising out of the spacecraft’s weight, distance travelled and the fuel it’s carrying.

As Amy Shira Tietel, an embedded journalist with New Horizons, explains in this video, the spacecraft is carrying enough fuel to get into Pluto’s vicinity – that’s about 77 kilograms of hydrazine. The weight of the entire space probe is 478 kgs including its cameras and scientific equipment, making it one of the fastest spacecrafts. Any more fuel on New Horizons would have made it heavier and considerably more expensive to launch. It would have also slowed down, making us wait many more years for data from Pluto. Without more fuel however, New Horizons will not have any propellant to burn to set it into Pluto’s orbit, much less land.

What New Horizons will do is whoosh past Pluto at a colossal 49,600 kilometers per hour and capture what it sees.