Bitcoin mining companies have been struggling under the weight of the year-long bear market, with collective debt expected to exceed $4 billion by the end of 2022, according to a report by Hashrate Index. Core Scientific is in the most serious situation. The company owes creditors $1.3 billion and has filed for Chapter 11 bankruptcy protection. Marathon Digital is owed about $851 million, but most of it is in convertible notes, meaning its creditors can exchange them for stock in the company.