Marita Moloney
Reporting from Washington DC

We're pausing our live coverage of the inquiry into the Titan sub implosion, after the former OceanGate scientific advisor concluded his evidence today.

Dr Steven Ross's 90-minute testimony followed earlier evidence from Renata Rojas, a mission specialist who was on the support vessel on the surface when the submersible vanished.

In an at times emotional testimony, she likened the Titan to the famous Apollo space programme and in a final closing statement she said she hoped "innovation continues".

Before the hearing started, we saw new footage released by the US Coast Guard showing the wreckage of the submersible, which imploded killing all five inside in June 2023, on the sea floor.

The public hearings began on Monday as part of a two-week inquiry by the Coast Guard into the disaster. The investigation has been going on for 15 months.

We'll be back tomorrow to bring you more from the inquiry, and until there there's plenty more to read across the BBC on the disaster:

• What we heard on the third day of the inquiry
• 'All good here': Titan sub's last messages before implosion
• Five key questions that remain

Thanks for joining us.

The hearing has finished for the day after testimony from Dr Steven Ross, the former scientific director of OceanGate.

We'll bring you a recap of events in a moment.

We're now hearing the testimony of Dr Steven Ross, the former scientific director of OceanGate, at the US Coast Guard inquiry into the company's deadly Titan voyage.

It follows evidence from mission specialist Renata Rojas, who told the hearing she "knew the Titanic dive was risky", but "never felt unsafe".

You can follow Ross's evidence on our stream above by clicking the watch live button - and we won't be bringing you regular text updates on the page.

Stephen Dowling
Deputy editor, BBC Future

Underwater explorer Victor Vescovo – who has travelled to the deepest part of the ocean, Challenger Deep, 15 times – says the Titan disaster could affect ocean exploration in the short term.

He says it could make people "more fearful of diving into the depths of the extraordinary ocean, the lifeblood of our world". But that would be the wrong response, he argues, akin to refusing to fly on an aircraft because of a plane crash.

"Those of us in the submersible community – the builders, pilots and researchers – have not hesitated in continuing to extensively dive in these vehicles, which should give everyone else confidence in their safety," he wrote in an article for BBC Future on the first anniversary of the disaster.

• Read more on what he had to say here

Mission specialist Renata Rojas has finished giving her testimony to the hearing - let's quickly look back at the key takeaways from what she has said today:

• Rojas told the public hearing her role is a volunteer position and is someone who stands by until someone needs help
• She admits she was aware the Titan submersible was not classified or registered and that its nature was for exploring
• "I knew the Titanic dive was risky, but I never felt unsafe," she told the hearing at Charleston County Council, South Carolina
• Tearing up at one point during her testimony, Rojas recalled seeing "five people smiling" as she described their final moments before going into the Titan and disappearing below the water surface last year
• She described the rescue efforts and protocol detailing that the team went into "go mode" when the Titan did not return on its scheduled time
• Rojas likened the Titan to the famous Apollo space programme and in a final closing statement she said she hopes "innovation continues"
• "Without taking that risk and the exploration, the world would still be flat," she added

Rojas once again was emotional as she made a personal statement at the end of her testimony.

After a long pause while she tried to compose herself, a recess was suggested. But Rojas insisted she would continue.

“What we have all gone through is still very raw," Rojas said.

“Nothing is going to bring our friends back.

"I hope that this investigation creates an understand that, with exploration there is risk. And without taking that risk and the exploration, the world would still be flat.

She goes on to say that marine expeditions are “significantly underfunded” and that she hopes private citizens will continue to fund them.

The hearing has now taken a recess, after which Dr Steven Ross – the former OceanGate Scientific Director, will be called as a witness.

Renata Rojas has just finished her testimony, giving a final tearful statement that "nothing is going to bring our friends back".

The hearing is taking another break. Stick with us, we will bring you more of that final statement from Rojas in a moment.

Rojas was just asked about her understanding of the term "experimental".

She replies that it meant "untested, new waters, completely new… never used underwater vehicles”.

Rojas says that no classification for carbon fibre subs existed, and that she was not surprised to hear that the Titan submersible was unclassed.

She claims that this was “similar" to the Apollo space programme.

"They tested by doing," says Rojas.

Next, Rojas is asked whether Stockton Rush (OceanGate's CEO who died when the Titan imploded), or others, ever explained to her the experimental nature of Titan?

"Yes," she replies.

Rojas is then asked if she was aware the Titan was not classified - again she answers "yes".

She tells the hearing she was unaware whether Titan was flagged to any nation.

Rojas is specifically asked about whether it had been flagged or registered by the Bahamas - to which she says she does not know.

Rojas is next asked if she was aware if maintenance was taking place on the Titan sub when it wasn't diving during the 2023 expedition.

She replies that people appeared to be working on it from the platform while it was in the water, but she was too far away to verify this.

We are back from the recess and Renata Rojas is asked if she felt "empowered to voice safety concerns".

"Yes," Rojas replies, adding she felt people were heard and OceanGate acted accordingly.

Turning to specific concerns related to some of her own dives, Rojas is asked about raising issues.

"I knew the risk I was taking and still decided to go," Rojas says.

And a reminder that you watch the hearing at the top of this page.

Before the break, Rojas was asked if a mission specialist was inside the submersible with the dome secured, would they be able to get out?

"No," she replied.

There's another short break in the hearing. So let's take a moment to look into some background on the submersible.

We recently been listening to testimony about the hull on the Titan.

For context, the sub’s hull was made of carbon fibre, an unconventional material for a deep-sea vessel.

Metals such as titanium are most commonly used as they are reliable under immense pressures.

You can see from the graphic below the key weaknesses on Titan.

Renata Rojas, a mission specialist for OceanGate, is asked about what the monitoring system looks like.

She describes it as similar to an "EKG", which stands for electrocardiogram - the device which visually shows a person's heartbeat.

As a mission specialist, she says she was able to watch the screen. She tells the hearing it would show spikes.

"It would mean the monitoring system heard a noise", she says, adding that if someone "knocked on the hull" or a whale was around, it would be picked up on the monitor as the device was sensitive to sounds in its vicinity.

Rebecca Morelle
Science editor

Image source, Reuters

The public hearings began with the release of exchanges between the Titan sub and the surface ship.

These were short text messages sent back and forth during the final dive.

Communications were a bit patchy during the descent, but a message from the sub about an hour into the dive said “All good here”.

A little after the passengers gave their location as being above the southeast of Titanic’s bow.

The final exchange was sent from 3,346m, saying Titan had dropped two weights - it would have released them to slow its descent as it neared the sea floor.

After that the messages stopped - the sub had imploded.

The US Coast Guard said that there was nothing in the messages that indicated that the passengers knew the sub was failing.

A log is now shown to the hearing of previous dives involving OceanGate.

Rojas is asked if there was a safety meeting after a dive in which the dome of the sub fell off.

She replies that there was, and it was decided that there needed to be better coordination between OceanGate and the crew of the ship from where it was launched.

Rojas also speaks about another technical incident on a test dive, and she says modifications were made following it to try to improve processes for the future.

Rojas explains that on expeditions "problems happen".

"You are in a very remote area, trying to do something very few people can do," Rojas explains, adding that teams have to adapt to situations which unfold in front of them.

"If you had a problem at the surface, you were at the surface," Rojas says.

Rojas then explains there was equipment onboard the Titan sub which allowed for life-support for 96 hours.

She recalls one previous and separate dive in which people stayed overnight on the sub because of bad weather.

Rojas is now asked if emergency drills were run on the Titan submersible.

She replies that this was done once inside the submersible.

Drills ranged from showing people where medicine was, to what to do if the pilot became incapacitated, she tells the hearing.

Rojas is asked whether people were told what to do if the sub was stuck on the ocean floor.

She replies that there were a number of options available, including releasing the legs or waiting for the tide to change.

The testimony turns to the rescue protocol while the Titan was below the surface.

"Usually they are allowed at least an hour," Rojas says, explaining those in the sub might have asked for more time to explore the Titanic shipwreck if they got there.

But, Rojas said the conversation turned to the sub being overdue.

"After another 15 minutes we're calling the coastguard," Rojas recalls conversations onboard the support vessel, as concerns started to rise at 6pm or 7pm local time.

She adds: "That's what we did. We went into 'go mode'".

Rojas said she heard nothing or saw nothing while on the bridge as communications with the sub appeared to be lost.