NASA Satellite Image: Pipeline ablaze outside Homs, Syria

This satellite image shows a pipeline fire in Homs, Syria. 

The pipeline, which runs through the rebel-held neighbourhood of Baba Amr, had been shelled by regime troops for the previous 12 days, according to two activist groups, the Local Coordination Committees and the Britain-based Syrian Observatory for Human Rights. 

The state news agency, SANA, blamed "armed terrorists" for the pipeline attack.

Picture: DigitalGlobe/AP

Gulf Oil Disaster: How big is the Deepwater Horizon oil disasterl?

The current size of the Deepwater Horizon spill is hard to measure exactly, but attempts can be made to estimate it.

Based on oil flow calculations from the National Oceanic and Atmospheric Administration, Dr Simon Boxall, a marine pollution expert, says a total current spill can be estimated at about 7,000 to 10,000 tonnes of oil. (See factbox below for how this was worked out.)

But such estimates should always carry a caveat, he says, as these can be affected by factors such as the condition of the rig, the well and the quality of information available.

In terms of lives lost (11 workers died in the rig explosion), financial cost and environmental damage, the Deepwater Horizon incident is clearly serious. But it is not one of the world's largest spills in terms of size alone.

In fact, based on the estimate above, it would not register in the largest 50 single incident, offshore oil spills that have occurred worldwide. Even the 1989 Exxon Valdez spill - despite the controversy and coverage - is not in the top 10.

However the potential for damage caused by Deepwater Horizon is apparent when looking at the events of June 1979 in the Bay of Campeche, also in the Gulf of Mexico.

In that spill, the exploratory oil well Ixtoc 1 suffered a blowout and wasn't capped until more than nine months later, having released 461,000 tonnes of oil in total.

ESA Envisat monitors Gulf oil spill proximity to Loop Current

As fears grow that the Loop Current in the Gulf of Mexico could soon catch the oil slick and drag it south towards coral reefs in the Florida Keys, scientists are monitoring the situation closely with ESA’s Envisat radar data.

By combining surface roughness and current flow information with Envisat Advanced Synthetic Aperture Radar (ASAR) data of the spill, SAR image analysts are able to detect the direction in which the spill boundaries can drift.

In these two ASAR images for 29 April and 2 May, advanced processing methods have been performed to display ocean surface roughness variations and Doppler-derived ocean surface radial velocities.

Merging this information provides insight into the spatial structure of the spill and its dispersion by the upper ocean turbulent flow.

Overview of the Loop Current in the Gulf of Mexico and its extension on the US East Coast called the Gulf Stream. Radial velocities (east-west component of velocity) are estimated from Envisat Advanced Synthetic Aperture Radar (ASAR) on this one-year composite.

The main path of the Loop Current and the Gulf Stream is highlighted by the red trajectory.

Go to ESA Envisat site for more info