The Nasa website tracking the balloon noted the ''balloon has been terminated'' and shows it somewhere near the western New South Wales/Victoria border with South Australia.
No more information on the end of what was hoped to be a 100-day mission was available last night, though a Nasa website on its scientific balloons said at the end of a flight a decision to end or ''terminate'' was made.
When the balloon system was over an area that was safe for ending the flight, a command was sent to separate the payload from the balloon.
The payload would parachute to the ground, while helium would escape through a large hole ripped in the balloon, which would descend separately.
Both would then be recovered.
The termination came not long after Nasa balloon programme chief Debbie Fairweather described the balloon as ''healthy and performing as designed''.
That was despite some unusual high-altitude changes in direction that had the balloon plotting an erratic course before flying over Australia.
It confused some observers on Saturday, one of whom even called police, after spotting the balloon in the sky above Victoria and thinking it was a UFO.
It was expected to spend a few days over Australia, before eventually continuing east.
The balloon was designed to be a reliable, low-cost means for conducting scientific investigations at mid-latitudes in a near-space environment.
On its test flight, it carried a 2268kg payload, including ballast and tracking and telemetry systems, at a constant altitude of 33.5km.
Before Australia, the balloon last flew over land on April 1 when it crossed the southern tips of Chile and Argentina.
Nasa had hoped to fly the balloon for more than 100 days.
The flight duration record is 54 days.
The balloon was one of 10 to 15 launched each year by Nasa's Wallops Flight Facility, based in Virginia, which manages the scientific balloon programme.
