The universe is thought to contain:

• only around 5% of ordinary matter
• 25% Dark Matter
• 70% Dark Energy

In other words, we don't know what 95% of the universe is made of.

Presence of Dark matter is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained unless more matter is present than can be seen.

Dark energy is an unknown form of energy which is hypothesized to permeate all of space, tending to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate.

What is Dark Matter and Dark Energy? by Kurzgesagt – In a Nutshell is an approachable introduction to the topic.

The question asks whether a Nobel Prize will be awarded before 2050 for work done primarily later than 2015, and directly related to explaining what Dark Matter is, as mentioned in the prize rationale.

If the prize is awarded before 2050 the question will close retroactively to the day before prize announcement. If the prize is not awarded before 2050, the question will close the day before the Nobel Prize announcement of 2049.