First, we searched about the challenge on the internet. Then we knew that Bennu is an asteroid in the Apollo group which can cause a potential danger to the Earth as it may hit in the 22th century. And we got our information from the internet from the following resources:
https://svs.gsfc.nasa.gov/4482
Finally, there are some challenges which faced us during the work which was like working in short time and to learn new things in short time was the hardest challenge faced us in our work.
SpaceApps is a NASA incubator innovation program.