Rating agency Standard and Poor's downgraded Greece's debt to junk status on Tuesday.
Greece has asked for 40 billion euros from fellow European Union governments and the International Monetary Fund, but it still faces huge debt payments. The New York Times reports that investors who buy Greek bonds face dwindling odds of getting their money back if Greece defaults or goes through a debt restructuring.
Junk status will make it much more expensive to borrow to make those payments. Portugal's rating was also cut, but is still above junk status.
That news, and worries that Europe's debt crisis could spiral out of control, pushed stocks lower today. The Dow Jones Average lost nearly 2 percent, closing at 10,991. The Nasdaq and S&P both fell by more than two percent.