The Sensex at the Bombay Stock Exchange dropped 177 points, to 18,256 in opening trade, today, amid weak global markets. Later, after falling more than 200 points at one stage, the Sensex recovered partially, but still stood a good 139 points, or 0.8 percent in negative territory, at 18,293, in afternoon deals, a short while ago. The 30-share index has already lost almost 440 points in the last two trading sessions.Other Asian markets in China, Japan, Singapore, Indonesia, Hong Kong and Taiwan were down by between 0.5 percent and 1.2 percent, today, on US debt worries, and on weaker-than-expected US economic data. In the US, the Dow Jones Industrial Average has dropped 1.6 per cent, overnight.